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I 



I 



THE CADET ENGINEER 



.i^7>0 



5" 



THE 



CADET ENGINEER 



OR 



STEAM FOR THE STUDENT 






BY 

JOHN H. LONG 

CHIEF ENGINEER UNITED STATES NATY 
AND 

E. H. BUEL 

ASSISTANT ENGINEER UNITED STATES NAVY. 




PHILADELPHIA: 
J. B. LIPPINCOTT & CO 

1865. 



Entered, according to Act of Congress, in the year 1865, by 

J. B. LIPPINCOTT & CO., 

in the Clerk's Office of the District Court of the United States for the Eastern 
District of Pennsylvania. 



RESPECTFULLY INSCEIBED 



TO THE 



onn^ (Bnjine^rs 



OF THE 



U. S. NAVAL AND MARINE SERVICE. 



PREFACE 



In this little work we have designedly avoided 
deep theoretical research, and have aimed rather to 
supply practical information. 

Theoretical works can be obtained in profusion, 
but treatises on the practical part of engineering are 
more rare. It is to be hoped that the idea of intro- 
ducing familiar topics, and things that (in common 
parlance) everybody knows, will meet with favor. 

The practical man wiU here find his experience in 
print, and to seekers for information these notes may 
be of some service. 

Norfolk Navy Yard, Virginia, 
March, 1865. 



• \ 



TABLE OF CONTENTS. 



Article Page 

Preface vii 

1. Description, advantages, and disadvantages of various 

kinds of Engines 11 

2. Description, advantages, and disadvantages of various 

kinds of Boilers 14 

3. Appendages to Engines and Boilers . . .IT 

4. The Paddle -Wheel 21 

5. The Screw Propeller . . . . .37 

6. Combustion of Coal 63 

7. Erection of Engines 69 

8. Steam 73 

9. Expansion of Steam 75 

10. Cut-Ofifs 88 

The Indicator 95 

The Slide Yalve 108 



11. 
12. 
13. 
14. 

15. 

16. 

17. 

18. 



Balanced Yalves . . . . . . .117 

Saturation of water in marine boilers, scale, and the 

means of preventing its formation . . 123 

Condensers and Feed- water Heaters . . . 132 
Relations of power (or fuel) and speed in steam 

navigation 140 

Management of Engines and Boilers at Sea . . 145 

Overhauling the Engines and Boilers in port . 161 

Index 173 

(ix) 



w 



THE 



CADET ENGINEER 



§ 1. Description, advantages and disadvantages of 
various hinds of Engines. 

Engines are either single-acting, rotative, or rotary. 

Rotative engines are classed as side-lever, beam, 
direct, back-acting, and geared engines. 

Direct-acting engines are termed oscillating, in- 
clined, horizontal, vertical, or trunk engines. 

The principal advantage of the side-lever engine 
is, that it is equally balanced. Its disadvantages 
are, its excessive weight and the space it occupies. 

The beam-engine is light in all its parts, occupies 
but little room, and is easily accessible. Its disad- 
vantages as a marine engine are, its extreme height, 
rendering it top-heavy, and occasioning great incon- 
venience, especially in a gale, and its liability to get 
out of line. 

Direct-acting engines are characterized by light- 
ness, and compactness of form. Their defects are, 
the shortness of stroke and of the connecting rod, 
which becomes sensible in practice, by an increased 
wear and tear of brasses and packing and a greater 

(11) 



12 THE CADET ENGINEEE. 

consumption of oil and tallow, as compared with the 
side-lever or beam engine. 

The advantages of the oscillating engine are, that 
it consists of few parts, occupies but little space, and 
is readily accessible for repairs. It has no disad- 
vantages worth mentioning, when well designed and 
built. 

The trunk engine admits of a longer connecting 
rod than some other forms of the direct-acting engine, 
and is composed of few parts. But it is very waste- 
ful of steam, as the large mass of metal of the trunk, 
moving alternately into the atmosphere and cylinder, 
must condense a portion of the steam. The trunk, 
also, requires large quantities of oil and tallow. 

The advantage of a back-acting engine, is the 
length of its connections. Its disadvantage is exces- 
sive weight, as compared with a direci>acting engine. 

Rotary engines have not hitherto been so successful 
as to warrant an extended notice. 

Single-acting engines are only employed for pump- 
ing, and are not suitable for use in a vessel. 

The advantage of geared engines is their slowness 
of piston speed, diminishing the wear and tear of the 
working parts, and operating very favorably in the 
case of the air and feed pumps. But they are larger 
than direct-acting engines, and besides, we have the 
weight of, and space occupied by the gearing. Still 
with all these disadvantages they are very successful, 
and the authors are of opinion that they are the best 
design of engines for screw-steamers. 



VAKIOUS KINDS OF ENGINES. 



13 



Among the varieties of the steam engine, we will 
notice Wright's, of which a sketch is given in Fig. 1. 




The cylinders are segmental, the piston rods being 
in the form of rings, as represented. 

Root's engine, Fig. 2, has one piston connected 




directly to the crank-pin. The pistons are rec- 
tangular, and work in a rectangular chamber. The 



14 THE CADET ENGINEER. 

piston B moves within the piston A and the crank- 
pin is connected to the former piston, at C. The 
piston B has a motion up and down, and the piston 
A a motion alternately to the right and left, so that 
the resulting motion is circular, a a a a are the 
steam ports, and hhhh the exhaust. 

§ 2. Descriptkm, advantages and disadvantages of 
various kinds of Bailers. 

Boilers are either vertical tubular, horizontal tubu- 
lar, flue, cylindrical, or a combination of these kinds. 

The advantages of the vertical tubular boiler are, 
its economic evaporation, and the facility and com- 
pleteness with which its heating surfaces can be 
scaled. Its disadvantages ar6, that it is often a very 
difficult matter to discover a leaking tube, and that 
considerable time is required to plug it after it is 
found ; for the boiler must be entirely blown down 
and cooled, and the man-holes opened, before the 
leak can be stopped. 

The advantages of the horizontal tubular boiler 
are, its less cost, and the fact that the tubes can be 
swept much more easily, rapidly, and completely, 
than the vertical tubes. If a tube leaks, it can be 
easily seen and plugged. Its principal disadvantage 
lies in the impossibility of keeping the entire surface 
of the tubes free from scale. 

The advantages of flue-boilers are, their economy 
in first cost, repairs and durability. Their disad- 



VARIOUS KINDS OF BOILERS. 



15 



vantages are, the space occupied and their weight, 
they being at least one-third heavier, and requiring 
one-third more room than tubular boilers of the same 
evaporative power. 

Cylindrical boilers are only used on steamers in 
the Western rivers, and can scarcely be classed among 
marine boilers. 

Fig. 3 represents the haystack boiler. This is a 




16 



THE CADET ENGINEER. 



round boiler, with vertical tubes and a spherical top. 
From its shape it requires but little bracing. All 
the parts are readily accessible for scaling and making 
repairs, and its evaporative power is very great. 

Mr. Dickerson's patent boiler is represented in 
Fig. 4. Above the furnace the fire passes around 
inclined tubes, filled with water. In the top of the 




boiler are vertical tubes, surrounded with water at 
the lower ends, and with steam at the upper ends. 



APPENDAGES TO ENGINES AND BOILERS. 17 

The object of these is to dry and superheat the 
steam. In the differential tubular boiler, introduced 
by Chief Engineer A. C. Stimers, U. S. N., the tubes 
are made of varying sizes, being largest in diameter 
at the lowest row, and decreasing as they ascend. 
The object of this is to equalize the temperature of 
the products of combustion entering the upper and 
lower tubes. 

§ 3. Appendages to Engines and Boilers. 

Under this head we will class all gauges, oil cups, 
and the like. 

It is usual for every boiler to be provided with a 
steam-gauge, so that if the stop-valves are closed, 
the pressure of the steam can be ascertained, and 
also for the convenience of the fireman and water- 
tender. Steam-gauges are made in various forms, 
but they can be put into two general divisions, mer- 
cury gauges and mechanical gauges. Of the mechani- 
cal gauges, Ashcroft's and Allen's are the most in 
use. In Ashcroft's gauge the steam acts upon a bent 
tube, elliptical in section ; and in Allen's a conical 
volute spring of finely tempered steel takes the 
pressure. The syphon gauge is the most common 
of the mercurial gauges, and is, doubtless, as good as 
any. It is well to have one of them attached to the 
engines or boilers as a test, for mechanical gauges 
lose their elasticity by use. The manometer gauge 



18 



THE CADET ENGINEER. 



is extensively used, but it is found that the glass 
tube gets foul very soon. Grimes's patent gauge, 
represented in Fig. 5, is said to be reliable, and to 
work very well. B is a closed top glass tube, inside 

of A, a larger glass tube 
open at the top, the bottom 
of it fitting closely into a 
vessel of mercury, C. The 
tube A is filled with alco- 
hol, and its upper end is 
connected with the steam- 
pipe. When there is no 
pressure on the alcohol, 
the mercury rises in the 
tube A to a h. By a 
pressure of steam equal 
to 10 lbs., the mercury is 
forced out of A to the 
level of the reservoir, C, 
and just begins to appear 
in the tube B. So up to 
10 lbs. we read the pres- 
sure on the left hand scale, 
and above that the pres- 
sure is indicated on the 
right hand scale by the height to which the mercury 
rises in the tube B. 

Besides the glass gauges and gauge-cocks, usually 
fitted to boilers, percussion gauges are sometimes 




APPENDAGES TO ENGINES AND BOILERS. 19 

attached, to be used when the boilers foam. A per- 
cussion gauge consists substantially of a cylinder, 
into which is fitted a piston, with a projecting rod. 
It is attached at the water level. If a boiler foams, 
the idea is to press the piston down, and observe at 
what point it strikes solid water. Whether any 
advantage is derived from this instrument is doubtful. 

The engines usually have steam and vacuum 
gauges, the steam-gauges being attached to the main 
steam-pipe. Gauges of the same general construction 
as those employed to indicate the pressure of the 
steam are also used to show the state of the vacuum. 
Thermometers are generally fitted to the hot wells. 
In the case of fresh water condensers, two ther- 
mometers are necessary, one for the discharge, and 
the other for the feed-water. Thermometers are also 
fitted, quite frequently, to show the temperature of 
the injection water. 

Most marine engines have counters to register the 
number of revolutions. Allen's counter is almost 
exclusively employed in this country. 

A gauge to show the amount of water in the bilge 
is very useful, and is often attached. When we add 
the clock, barometer, and engine-room thermometer, 
the list of appendages is nearly complete. 

Engines should be fitted with oil cups on all 
journals, and also on the steam-chests and cylinder 
covers. Oil or tallow can readily be introduced into 
the cylinder of a condensing engine by letting the 



20 



THE CADET ENGINEER. 



pressure of the air force it in, when there is a vacuum 
in the cylinder. For steam-chests and high pressure 
engines, the oil cup represented in Fig. 6 is largely 
used. The reservoirs, A and B, are separated by a 
valve, C. This is kept against its seat by a spiral 
spring, and can only be opened by a downward pres- 
sure. The valve D, when 
shut, cuts off commu- 
nication between the 
steam-chest or cylinder, 
and the reservoir B. The 
valve D has a square 
stem, which fits into a 
socket in the stem of the 
valve C. By turning 
around this upper stem, 
the valve D is screwed 
down to its seat, the valve 
C remaining closed. It 
will be seen that the valve 
D must be shut to enable 
the valve C to be opened. 
When not in use, all the 
parts of the oil cup are as represented in the figure. 




THE PADDLE-WHEEL. 



21 



DFia.7. 



The operation is as follows : close the valve D, and 

open the valve E, to let steam 

escape from B. Fill A with 

oil, and open the valve C, to 

let the oil run down into the 

reservoir B. Then close E, 

and open D, when the oil will 

run down into the cylinder or 

steam-chest. 

Fogle's oil cup, sketched in 
Fig. 7, has no valves or cocks. 
The cup slides up and down 
on the tube C, by raising or 
lowering the handle G. Sup- 
pose the reservoir A to be 
filled with oil. By raising the 
cup, the steam escapes from 
B through the pipe D, and 
the oil runs into B. On re- 
turning the cup to its original 
position, the oil will run into 
the cylinder through the pipe E 




§ 4. TJie PaddU'Wheel. 

Although the plans for applying the power of the 
engines to propel ships through the water have been 
numerous and varied, the only two that have stood 
the test of time are paddle-wheels and screw pro- 
pellers. Paddle-wheels are of two general kinds, 



22 



THE CADET ENGINEER. 



radial and feathering wheels. In the case of the 
radial wheel, the floats enter and leave the water 
obliquely, only being vertical in the centre of the 
arc of immersion. In the feathering wheel the floats 
are governed by mechanism, which causes them to 
enter and leave the water in a position perpendicular 
to the direction of their motion. Fig. 8 is a sketch 
of a feathering wheel, which will show the arrange- 
ment by which the floats are governed. 




The Manley paddle-wheel, which has lately been 
the subject of many experiments, and is considered 
a very successful variety of the feathering wheel, is 



THE PADDLE-WHEEL. 23 

represented in Fig. 9. This wheel has only six or 
eight floats. Each float is secured to a rock shaft, 
to which a crank is attached. The feathering 
mechanism is a frame, eccentric to the main shaft, 
connected with each of the cranks by an arm. Each 






float is secured to the rock shaft below the centre, so 
as to divide the pressure on the float equally between 
the feathering mechanism and the adjacent side frame 
of the wheel. 

The following is an extract from the pamphlet 
issued by the Manley Paddle-Wheel Company : 



24 THE CADET ENGINEER. 

" This wheel is the first machine for marine pro- 
pulsion, which, by its action and application of 
power, has imitated the Indian's paddle, and has 
conformed to the first great principle necessary to 
be observed in propelling a vessel through the water, 
by obtaining the proper resistance for the power 
upon the water. The Indian reaches forward and 
drops the blade of his paddle into the water verti- 
cally, and instantaneously exerts his force in a 
direction opposite to that in which he wishes the 
boat to move, and perpendicular to the line of floata- 
tion, then withdraws the blade entirely from the 
water and repeats the operation, at all times keeping 
his paddle vertical while it is in the water. * * * * 
This wheel does for the great steamship what the 
Indian's paddle does for his boat, and even in greater 
perfection. It drops a paddle into undisturbed water, 
forces it backward or forward, as the case may be, in 
a direction exactly perpendicular to the line of floata- 
tion, and as it is being withdrawn from the water, 
another paddle is entering far ahead, and grasping 
resistance entirely unused by the preceding paddle, 
and this operation is certain and constant while the 
power is applied. There is no tearing of the water, 
no paddle following water which has been put in 
motion by a fellow paddle, no displacing of water, 
either upward or downward." 

There have been numerous devices for causing the 
floats of the radial wheel to enter the water with as 
little resistance as possible, and on leaving the water 



THE PADDLE-WHEEL. 25 

not to lift any of it. The principles on which these 
wheels are constructed appear to be very good, but 
they have not yet displaced the common flat float. 

Although the feathering wheel produces more use- 
, ful effect, with the same application of power, than 
the radial wheel, there are many practical objections 
to its use; the most prominent of which are the 
increased first cost, the excessive weight, and the 
frequent overhauling that they require. 

The action of a radial wheel in propelling a vessel 
resembles that of the wheel of a carriage. While 
the wheels of a carriage, however, propel the car- 
riage the whole distance due to their rolling motion, 
paddle wheels do not propel a vessel a distance due 
to their velocity at the circumference. But the 
velocity of some circle within the circumference will 
be equal to the speed of the vessel, and we call this 
circle the rolling circle. 

Example. — Suppose a side-wheel steamer is pro- 
pelled through the water at the rate of 12 statute 
miles an hour, the engines making 19 revolutions 
per minute; what is the diameter of the rolling 
circle ? 

The distance passed over by the vessel in an 
hour is 

5280 X 12 = 63360. 

Now the wheels make 19 X 60 =z 1140 revolu- 
tions per hour, and the circumference that will pass 
over 63360 feet in 1140 revolutions is 63360 ^ 1140 
zz 55.58 feet. The diameter corresponding to this 



26 THE CADET ENGINEER. 

circumference is 55.58 -4- 3.1416 = 17.69 feet, which 
is the diameter of the rolhng circle. 

From the fact that 5280 -j- 60 = 88, is a constant 
number to be introduced into all calculations for the 
diameter of the rolling circle, we can give the follow- 
ing rule. Multiply the speed of the vessel in miles 
per hour by 88, and divide this product by 3.1416 
times the number of revolutions of the wheels per 
minute. This will give the diameter of the rolling 
circle. By this rule the solution of the preceding 
example will be, 

(12 X 88) ^ (19 X 3.1416) = 17.69 feet, the diam- 
eter of the rolling circle. 

In this rule the speed of the vessel is given in 
statute miles, for the sake of having the constant 
quantity, 88, a whole number. When the speed is 
given in nautical miles, we have only to multiply by 
1.15, and the result will be the speed in statute 
miles. 

That point in each float of a paddle-wheel at 
which the whole pressure acting on the float being 
applied would produce the same effect as when act- 
ing on the whole float, is called the centre of presmre. 
For a radial wheel we usually take the centre of 
pressure at about I of the width of the float from 
the bottom. This is on account of the greater 
velocity of the outer extremity of the float, causing 
the resistance at the circumference to be greater than 
at the inner extremity. The following empirical 
formula is also frequently employed to find the 



THE PADDLE-WHEEL. 27 

position of the centre of pressure in a radial wheel. 
Subtract the diameter of the rolling circle from the 
diameter of the paddle-wheel, and add half the differ- 
ence to the width of the float ; raise the sum of these 
two numbers to the fourth power, and divide the 
result by four times the width of the float ; find the 
cube root of the quotient, then subtract from this 
root half the difference between the diameters of the 
wheel and rolling circle ; the remainder will be the 
required quantity, or the perpendicular distance of 
the centre of pressure from the inner extremity of 
the float. There is one thing to be remembered in 
using this rule, that the rolling circle must have a 
constant diameter. The average diameter of the 
rolling circle can easily be obtained by experiment 
for any particular wheel, and then it is fixed. With 
this understanding, the rule is tolerably accurate. 

Example. — Find the position of the centre of 
pressure of a radial wheel, from the following data : 
diameter of wheel, 26 feet; width of float, 30 inches; 
revolutions of engines per minute, 18 ; speed of vessel 
in knots per hour, 10. 

10Xl-15zzll.5, speed of vessel in statute miles ; 
(11.5 X 88) -^ (3.1416X18) = 17.89, diameter of 
rolKno' circle. 



Now we are ready to apply the rule. Half the 
fferenc 
circle is 



difference of the diameters of the wheel and rolling 



26 — 17.89-^2 = 4.000. 



28 THE CADET ENGINEER. 

The width of the float being 2.5 feet, we shall 
have 

(4.055 + 2.5) ' -r- (2.5 X 4) = 184.625, 

cube root of 184.625 = 5.694. 

5.694— 4.055=1 1.639 =zl foot, 7f inches, distance 
of centre of pressure below top of float. 

It must be observed, that as a float enters and 
leaves the water, it is only partially immersed, and 
as we wash to find the mean centre of pressure, we 
must consider this in making our calculation. Let 
us divide the arc of immersion into a number of 
equal parts, which will represent different positions 
of a float in its passage through the water. When 
entering, it will require to be about half immersed 
before it will experience any decided resistance. 
Suppose the number of divisions of the arc to be 25 ; 
then for the first and last positions of the float, we 
must calculate the centre of pressure for half of the 
float; for the other 23 positions we make the calcu- 
lation for an immersed float. For the immersed float 
the centre of pressure is 30 — 19tz=:10l inches from 
the lower extremity. For the half immersed float, 
it will be sufficiently accurate to call the centre of 
pressure 101 -r- 2 zz 5j^ inches from the lower ex- 
tremity. The mean centre of pressure will then be 

(101 X 23 + 5^1^ X 2) ^25 1= 9^^ inches from lower 
extremity of float. 

If we use the other empirical rule, that the centre 
of pressure is i of the width of the float from the 
lower extremity, we shall have 30 -^ 3 = 10 inches, 



THE PADDLE-WHEEL. 29 

as the distance of the centre of pressure from the 
lower extremity of the immersed float, and 15 -J- 3 
zz 5 inches, as the distance from the lower extremity 
of the half immersed float. The position of the mean 
centre of pressure will then be 

(10X23 + 5X2) ^25zz93^ inches from lower 
extremity of float. A mean of these two results give 
us 9|J inches as the position of the mean centre of 
pressure. 

For a feathering wheel the position of the centre 
of pressure below the surface of the water, for the 
immersed float, is found by taking f of the diflerence 
of the cubes of the immersions of the upper and lower 
extremities of the float, divided by the diflerence of 
the squares of these immersions. For the half im- 
mersed float, the centre of pressure is i of the im- 
mersed width from the lower extremity of the float. 

Example. — Find the centre of pressure of a feather- 
ing wheel, having the same diameter and width of 
float as the radial wheel in the preceding example. 

Divide the arc of immersion into 25 equal parts, 
as before, and find the immersion of the lower ex- 
tremity of the float in the 23 intermediate positions. 
From these different distances we can get the mean 
immersion. Let us suppose the operation completed, 
and that we find the mean immersion to be 61.3 
inches from the surface of the water. The mean 
immersion of the upper extremity of the float in 
these intermediate positions will be 61. 3 — 30=z31.3 



30 



THE CADET ENGINEEK. 



inches. Hence the mean centre of pressure for the 

immersed float will be 

f of (61.3^ — 31.3^) -4- (61.3^ — 31.3^) = 47.82 

inches from the surface of the water, or 61.3 — 47.82 

z= 13.48 inches from the lower extremity of the float. 

For the half immersed float the centre of pressure is 

15 -^- 3 zz 5 inches from the lower extremity. Hence 

the mean centre of pressure is 

(13.48 X 23 + 5 X 2) -f- 25 = 121 inches from the 

lower extremity of the float. 

In the case of the radial wheel, part of the power 

applied is lost by oblique action, and part by slip. 

We will show the method of determining these losses. 

Let us first consider the loss by oblique action. 
Let A C (Fig. 10) represent the position of a float 

of a radial wheel, making an angle, BAG, with the 

surface of the water in which it is immersed. Now 

the float, in passing through the water, has a pressure 
in proportion to its depth, A C, 
and produces an effect varying 
directly as the pressure, so that 
the power exerted varies as the 
square of A C. But on account 
of the float passing through the 
water obliquely, the only power 
producing useful effect will be 
that developed by the vertical 



f-^"'- A 




component (A D) of A C. The power developed by 
the horizontal component, C D, acts in forcing the 
water downward, if the float is moving to the right, 



THE PADDLE-WHEEL. 31 

and lifts the water, if moving to the left ; therefore all 
this power is lost. If we make A C equal to one, then 
by trigonometry C D, the component, producing no 
useful effect, is equal to the sine of the angle CAD. 
This gives us a very simple method of determining the 
loss by oblique action. If the power developed by 
A C is one, the power lost by oblique action, since it 
varies as the square of the arm producing pressure, is 
equal to the square of the sine of the angle CAD. 
Thus, let the angle CAD equal 45°. The sine of 45° 
is. 70711, and the square of this is .5, so that .5 or 50 
per cent, of the power applied to the float is lost, 
when it makes an angle of 45° with a line perpen- 
dicular to the surface of the water, and only 1 — .5 
zz .5, or 50 per cent, of the power applied is effective 
in propelling the vessel. If the angle C A D is 30°, 
its sine is .5, and the loss by oblique action, or the 
square of the sine, is .25, or 25 per cent, of the power 
applied to the float, and 100 — 25 = 75 per cent., 
produces useful effect. If the float A C coincides 
with the vertical component A D, as it wdll when 
the float is in its lowest position, there will be no loss 
from oblique action, as will be at once apparent. 
Now we see that the loss from oblique action varies 
at every position of the float. Hence we must find 
the mean of the losses at various positions. 

Example. — Let us have a radial wheel, whose 
floats are immersed to such a depth that the angle 
formed by the intersection of the positions of the 



32 THE CADET ENGINEER. 

entering and emerging floats, at the centre of the 
wheel, is 100°, required the loss by oblique action. 

We will divide one-half of the immersed arc of 
the wheel into any number of equal parts, and draw 
lines from each point of division to the centre of the 
wheel. We shall thus determine various positions 
of the immersed float. The positions in the other 
half of the immersed arc would be exactly similar, 
and we shall not need them in the calculation. Now 
find the per cent, of loss by oblique action at each 
of these positions of the float, multiply it by 2 for 
the whole arc, since we only made the calculation 
for one-half, and take the mean, which will give the 
mean per cent, of loss. We will find the per cent, 
of loss for every increase of 2° in the angle between 
the float and perpendicular. At the centre of the 
arc, where the float is vertical, there is no loss. 
When the float makes an angle of 2° with the ver- 
tical, the loss is the square of the sine of 2°, or 
.003045, which equals .3 per cent, of the power 
applied. When the angle of the float with the ver- 
tical line is 4°, the loss equals the square of the sine 
of 4°, or .004804, .48 per cent, of the power applied. 
Continuing the operation for every angle, increasing 
by 2° up to 50°, we have 

(0 + .3 + .48 + 1.09+1.93 + 3.01 + 4.32-f 5.85 + 
7.59 + 9.54 + 11.69 + 14.11 + 16.54 + 19.22 + 22.05 
4. 25 + 28 + 31.27 + 34.54 + 37.9 + 41.32 + 44.77 
+ 48.24 + 51.73 + 55.22 + 58.67) X 2 = 1148.4. 

Since we have made the calculation in 25 difierent 



THE PADDLE-WHEEL. 83 

positions of the float, exclusive of the vertical posi- 
tion, or at 25 + 1 + 25 = 51 positions for the whole 
immersed arc, 

1148.4-^-51 = 22.517 per cent, of power lost bj 
oblique action. 

The following rule is derived bv ex|)eriment, and 
is found to give the result more accurately than the 
preceding method. Multiply the sine of the angle 
of immersion, or the angle made by the extreme 
positions of the immersed floats with each other, by 
25, and subtract the product from 50. The re- 
mainder is the per cent, of loss by oblique action. 

In the preceding example, the angle of immersion 
is 100°, and the sine of 100° is .98481. Hence the 
per cent, of loss by oblique action is, 

50— (25 X. 98481) =25.379. 
By this rule the per cent, of loss is slightly greater 
than by the first method ; but if the divisions of the 
arc had been small enough in the first case, the two 
results would have coincided more nearly, for the 
rule just enunciated is merely a method of finding 
the per cent, of loss, when the divisions of the 
inmiersed arc are exceedingly small. 

As the per cent, of loss by oblique action depends 
directly on the angle of immersion, it is evident that 
this per cent, will be greater, the greater the immer- 
sion for wheels having the same diameter. 

Let us now consider the loss of efiect from slip. 
Suppose a steamer has radial wheels with a diameter 
of 26 feet; that the width of the floats is 30 inches; 

3 



34 THE CADET ENGINEER. 

that the vessel has a speed of 12 statute miles per 
hour, and that the wheels make 18 revolutions per 
minute ; what is the per cent, of slip ? 

By the method shown in a previous part of this 
article, we find the diameter of the centre of pressure 
of the wheel to be 24 feet, 41 inches. The difference 
between the distance passed over by a wheel of this 
diameter and the speed of the vessel, is the slip. In 
the example under consideration, the vessel passes 
over 12X5280 = 63360 feet per hour, while the 
speed due to the velocity of the centre of pressure is 
24.3958X3.1416X18X601=82749.6. The slip, 
therefore, is 82749.6 — 63360 = 19389.6 feet, or 
(19389.6 X 100) -T- 82749.6 = 23.4 per cent, of the 
speed due to the wheels. 

This 23.4 per cent, is not the per cent, of loss from 
slip, since there can be no loss from slip, for the 
component of the float that produces no useful effect. 
The power that exerts no propelling force, can have 
no slip, since slip has a direct relation to the speed 
with which the floats force a vessel through the 
water. Now we have already found the loss by 
oblique action to be 25.37 per cent, of the power 
applied to the wheels. Therefore, only 100 — 25.37 
zz 74.63 per cent, of the whole power produces pro- 
pelling effect. So we see that the loss of effect from 
slip is 23.4 per cent, of the power producing useful 
effect, or 74.63 X -234 = 17.46 per cent, of the 
whole power applied to the wheels. 

Summing up the losses of effect, we have 100 — 



THE PADDLE-WHEEL. 



35 



(17.46 + 25.37) =57.17 per cent, of the whole power 
applied, producing useful effect, and 17.46 + 25.37 = 
42.83 per cent, of the power, lost by slip and oblique 
action. 

In the case of a feathering wheel, there is a loss 
of useful effect, from three causes : friction of the 
mechanism for feathering the floats, slip, and drag, 
caused by the vessel going faster than the entering 
and leaving float. Suppose A C B D, Fig. 11, to 
be the circle de- 
scribed by the 
centre of pres- 
sure of a feather- 
ing float. Now 
if there is no slip, 
the float, which 
is vertical all the 
time, will propel 
the vessel the 
distance A D B, 
while travelling 
the horizontal 
distance, A B. Thus, we shall have the vessel 
going through the water faster than the floats, and 
the latter will therefore be dragged, and there will 
be a per cent, of loss, in proportion to the difference 
between A D B, and A B. But if there is slip, the 
loss from drag will be the difference between A B, 
and A D B diminished by the slip. In actual prac- 
tice there will be no drag, unless the wheel has very 




S6 THE CADET ENGINEER. 

great immersion, or an exceedingly small slip. If 
we take a feathering wheel, having the same diameter 
of centre of pressure, the same immersion, size of 
floats, and per cent, of slip, as the radial wheel pre- 
viously considered, we shall find that instead of any 
drag existing, the floats will move faster horizontally, 
than the vessel travels. The chord of the immersed 
arc, or the distance passed over by a float horizon- 
tally in this case, is 18.67 feet. The arc of immer- 
sion, or the distance passed over by the centre of 
pressure, while the float moves 18.67 feet horizontally, 
is 21.27 feet. So if there were no slip, the loss from 
drag would be 21.27 — 18.67 = 2.6 feet, or 2.6 X 
100 -^ 21.27 z= 12.3 percent. But according to our 
supposition, there is 23.4 per cent, of slip ; so that 
the vessel only travels 21.27— (21.27 X -234) zz 
15.19 feet, while the float travels horizontally, 18.67 
feet. Therefore, the float moves horizontally, 18.67 
— 15.19 = 3.48, or 3.48 X 100 -f- 18.67 = 18.6 per 
cent, faster than the ship travels. 

If the friction of the feathering mechanism is not 
considered, the total loss of effect in the present case, 
is 23.4 per cent., which is 42.83 — 23.4 = 19.43 per 
cent, less than in the radial wheel. 

The friction of the feathering mechanism can only 
be determined by experiment. In the examples 
under consideration, as both wheels have the same 
per cent, of slip, and the feathering wheel utilizes 
19.43 per cent, more power than the radial, it follows 
that, all other things being equal, a vessel fitted with 



THE SCREW PROPELLER. 37 

feathering wheels should go just as fast as a vessel 
fitted with radial wheels, with an expenditure of 
19.43 per cent, less power. Thus, if the engines of 
the latter ship exerted 1000 horse power to produce 
a speed of 10 knots, the engines of the vessel fitted 
with the feathering wheels, should -only exert 1000 
— (1000 X .1943) = 805.7 horse power, to produce 
the same speed. Suppose, liowever, that the actual 
horse power required in the latter case Avas 900. 
Then we have 900 — 805.7 z= 94.3 horse power, or 
94.3 X 100 -^ 900 = 10.5 per cent, of the whole 
power developed by the engines, expended in over- 
coming the friction of the feathering mechanism. 
This gives us 100 — 10.5 = 89.5 per cent, of the 
whole power, transmitted to the wheels. Here we 
have a loss of 89.5 X -234 = 20.94 per cent, from 
slip ; so that the total loss of effect in the feathering 
wheel, is 20.94 + 10.5 z= 31.44 per cent, of the power 
transmitted. Hence, the gain over the radial wheel 
is 42.83 — 31.44 = 11.39 per cent. 

§ 5. The Screw Pi^opeller. 

A screw is generated by the revolution of a line 
or surface, called the generatrix, around a cylinder, 
the generatrix passing through the axis of the 
cylinder, and advancing along the axis as it revolves. 

If the axial motion has a constant ratio with the 
circular motion, a true screw is generated ; but if the 
axial motion is continually increasing, while the cir- 
cular motion is constant, the result is a screw^ with 
an expanding pitch. 



38 



THE CADET ENGINEER. 



The pitch of a screw is the axial distance travelled 
by the generatrix, while it makes one revolution 
around the cylinder. 

In the case of a screw propeller, the hub takes the 
place of the cylinder, and the blades are threads of 
screws, where only a fraction of the pitch is employed. 
The blades are supposed to be generated by lines, 
and then the proper thickness is put on. 

Now suppose that we generate a screw thread 
with a line, and that the generatrix makes one 
revolution. 

Suppose, also, that the outer extremity of the 
generating line traces its path on the surface of a 
cylinder, and that the cylinder be then developed, 
so as to coincide with a plane surface. 

In the first place, let us generate a true screw. 

If we suppose the generating line to start from the 
point A, Fig. 12, when its path is developed; it will 




appear as the straight Hne A B ; for it has travelled 



THE SCREW PBOPELLER. 39 

in an axial direction, the distance A C, and in a 
circular direction, the distance C B, with a constant 
motion. So we see that A C represents the pitch, 
and A B the thread of the screw. 

The angle B A C, is called the angle of the screw, 
and it is evident that this angle is constant, whether 
the whole pitch, or only a fraction, is employed. 

This angle, BAG, although called the angle of 
the screw, is only the angle at the periphery. Sup- 
pose, while the outer extremity of the generatrix 
moves around the axis, a distance C B, the other 
extremity, or the end that touches the cylinder, 
moves a circular distance C D. Then the path 
described by this extremity of the generatrix, since 
it moves the same distance A C, in an axial direction, 
is evidently A D. So we have another angle D A C, 
of the blade, and this is called the angle at the hub. 

It will readily be seen that the angles of the blade 
vary at every point of the circumference, and the 
angle B A C, is only called the angle of the screw 
from the fact of its being used in the construction 
of a propeller, as will be seen hereafter. 

Now let us take the case of a screw with an 
expanding pitch. The generatrix starts from the 
point A, Fig. 13, with a pitch D B, which increases 
to C B, by the time the generatrix has made one 
revolution. We see that at the commencement of 
the motion of the generatrix, it takes the path A D, 
and at the end of one revolution, takes the path A 
C, so that a curved line, A E C, drawn tangent to 



40 THE CADET ENGINEER. 

these two paths, will represent the course of the 
generatrix. 




A C B is now called the angle of the screw, and 
is used as a guide for the sweep, in constructing the 
propeller. 

In this form of expanding pitch, we say that the 
pitch expands from forward to after part of blade, 
or vice versa. The pitch may also expand from 
hub to periphery, or the reverse. All such screws 
are termed irregular. 

The advantage claimed for a propeller with pitch 
expanding from forward to after part of blade, is as 
follows : The part of the blade entering the water, 
acts upon water at rest, while the part of the blade 
following, acts upon water set in motion by the first 
part of the blade, and its pitch is increased, so as to 
encounter a resistance equal to that of the entering 
edge of the blade. 



THE SCREW FROPELLEE. 41 

Whether, after the propeller has made one revo- 
lution, and all parts of the blade have set the sur- 
rounding water in motion, the gain from this ex- 
panding pitch is as decided as has been alleged, is a 
question. 

The designers of propellers, whose pitch expands 
from hub to periphery, claim, and with very good 
reason, that the part of the blade near the hub is of 
very little service in propelling the vessel, and that 
it is a gain to make this part move through the water 
with as little resistance as possible. But this can be 
accomplished, and frequently is, by cutting away 
that portion of the blade nearest the hub, and in- 
creasing the surface at the periphery. 

To still further diminish the prejudicial resistance, 
the hub is frequently made spherical. Sometimes it 
is made very large, so as to take the place of that 
portion of the blade which has but little propelling 
effect. 

In view of the facts that all these modifications 
of the propeller give good results, and that various 
bujlders, each designing propellers with distinct fea- 
tures, have been successful in the results obtained 
from their designs, it seems impossible to give rules 
and formulae by which the best propeller may be 
constructed. 

The authors of this work incline to the opinion 
that a true screw can be constructed to produce as 
good results as any other. 

We will now complete the definitions connected 



42 THE CADET ENGINEER. 

with the propeller, and at the same time take into 
consideration a few general principles of proportioning 
the parts. 

The slip of a propeller is the difference between 
the actual distance travelled by the ship, and the 
distance it should have travelled by the motion of 
the propeller. 

Thus : suppose the propeller to have a pitch of 
25 feet, and to make 50 revolutions per minute; 
then the distance in knots it should move in an 
hour is 

(50X60X25)-^6027z=12.4. 

But the ship, we suppose, has an actual speed of 
11 knots, consequently, 

(12.4 — 11 = 1.4 knots z=. slip, or, 

(1.4 X 100) -7- 12.4 1= 11.3 per cent. slip. 

We see that the slip is caused by the propeller 
working in a yielding medium, so we can define the 
slip of a propeller as the motion of the water astern. 
In designing a propeller, we can only allow for the 
slip under favorable circumstances. We know, by 
experience, that in good weather the slip of a well- 
designed propeller is from 10 to 15 per cent. But 
in the case of a strong head wind and sea, while the 
revolutions of the propeller remain unchanged, the 
speed of the vessel is materially decreased. This is 
so, from the fact of water being a yielding medium, 
and from the manner in which the blades enter the 
water, so that, when a head wind and sea prevail, 
the resistance to the motion of the propeller is not 



I 



THE SCREW PROPELLER. 43 

increased, but there is more motion of the water 
astern, in direct proportion to the increased resistance 
to the passage of the ship through the water. 

A propeller with a small pitch has its slip slightly 
reduced, particularly in the case of adverse winds 
and seas, from the fact that the resistance to its 
motion is more in the direction of its propelhng face 
than when the pitch is greater. But when a small 
pitch is employed, an increased number of revolu- 
tions must be made, to keep up the speed of the 
vessel, and there is a practical hmit to this. 

When a ship has a greater speed than is due to 
the propeller, we say that the propeller has negative 
slip. Such a case may occur with a fair wind, and 
all sail set, but in a calm its occurrence seems rather 
improbable. Still, such a result might be effected 
by the springing or twisting of the blades, thereby 
causing an increase of pitch. In the generality of 
screw steamers, however, we will venture to assert 
that negative slip is a thing unknown. 

Propellers are constructed with the number of 
blades varying from two to four, and sometimes ex- 
ceeding the latter number. The number should not 
be so great that the amount of water between two 
contiguous blades would be reduced so as to lessen 
the resistance. 

Hence small propellers, by reason of their small 
surface, are usually constructed with four blades, 
while large ones rarely have more than three. 

The area of the screw's disc is the area of a circle 



44 THE CADET ENGINEER. 

having the same diameter as the propeller. It is 
evident, that if the propeller were to make one revo- 
lution, and the surface of the blades were then to 
be projected upon a plane surface perpendicular to 
the axis, this projection would be equal to the area 
of the screw's disc. Now, as the propelling force of 
the screw is only exerted in the direction of the axis, 
this area represents the thrusting surface of the pro- 
peller. The thrust is usually ascertained by the 
application of a dynamometer to the shaft. 

The theoretical thrust is ascertained as follows : 
If the piston and propeller had an equal speed, then 
the theoretical thrust would be the pressure on the 
piston. But as this is seldom the case, we find the 
speed of the piston in feet per minute, and also the 
speed of the propeller, in an axial direction, in the 
same time. Then the speed of the piston, divided 
by that of the propeller, is the ratio of the two 
speeds. Multiply this by the pressure on the piston, 
and we have the theoretical thrust in pounds. 

Example. — Required to find the theoretical thrust 
of a propeller, driven by a single direct-acting engine, 
having a piston 60 inches in diameter, and a stroke 
of 3 feet. Let the effective pressure of steam be 
25 pounds, the number of revolutions 55, and the 
pitch of the propeller, 22 feet. 

2827.4 X 25 = 70685 = pressure on piston, in pounds. 
2X^X^^ = 330 = speed of piston, in ft. per minute. 
22 X ^^ = 1210 z= speed of propeller, in ft. per minute. 
330 -f- 1210 = 1^1 = ratio of speeds. 



THE SCREW PROPELLER. 45 

70685 X 1^ = 19259. 5 = thrust of propeller, in pounds. 

The dynamometer thrust will be less than this. 
The difference between the two shows the pressure 
required to overcome friction and other prejudicial 
resistances. 

It is often necessary to measure a propeller for 
purposes of construction, and it is also useful to do 
so for further reference. We will therefore explain 
the method. 

The object is to obtain the development of the 
thread of the screw, and form a triangle, as shown 
in Fig. 12. (The measurements of the hub and 
diameter are so simple as to require no explanation.) 

As the blade at its extremity is frequently rounded 
off on the corners, it is better to assume a point a 
little within the circumference, to make the measure- 
ment. 

Having assumed a point, measure its distance from 
the centre, and with a piece of chalk draw a line to 
represent the helix described b}' the generatrix, at 
that distance from the centre. This is the line that 
we wish to develope. From one extremity of this 
helix, hold a straight-edge parallel to the axis of the 
propeller, and from the other extremity, hold a 
straight-edge perpendicular to the first. Measure 
the lengths of these two straight-edges^ between the 
points of their intersection and the extremities of 
the helix. 

Our measurements are then complete. The first 
distance is the fraction of the pitch, or the motion of 



46 THE CADET ENGINEEE. 

the generatrix in an axial direction, and the second 
is the fraction of the circumference, or the motion of 
the generatrix in a circular direction. By laying 
down these two distances at right angles to, and 
intersecting each other, and connecting their extremi- 
ties, we have the thread of the blade, and the triangle 
is complete. 

Now we must find the whole pitch, having the 
fraction given. Ascertain what is the circumference 
described at the distance from the centre at which 
we assumed our point, and then make the following 
proportion : The measured fraction of the circumference : 




the whole circumference : : the measured fraction of the 
pitch : tlie whole pitchy or. Fig. 14, as A B : A C : : 
B E : C D. 

Example. — Suppose, that on taking measurements 
in the manner indicated, we find the fraction of the 
pitch to be 18 inches, the fraction of the circum- 
ference, 3 feet, and that we have made the measure- 



I 



THE SCREW PROPELLER. 47 

ments 5 feet from the centre of the propeller. Now 
the circumference whose radius is 5 feet, is 31.41 ; 
hence, 

As 3 : 31.41 : : 1.5 : 15.7 feet, whole pitch. 

In the preceding discussion, we have assumed that 
the propeller we were measuring, was a true screw. 
But the principle of the measurements is the same 
in all cases, and it only remains to show the methods 
of determining whether the propeller has an expand- 
ing pitch. 

Take two measurements for the pitch, one near 
the hub, and the other near the periphery. That 
will show whether the pitch expands from hub to 
periphery, or is constant. Then divide the helix 
that is drawn near the periphery, into two equal 
parts, and take the extremities of each of these parts 
as the points at which to set the straight-edges. We 
shall thus determine whether the pitch expands from 
forward to after part of blade. 

In all cases where the pitch of a propeller varies, 
we must find it at various points of the blade, and 
take the mean to use in calculations where the pitch 
is introduced. 

We will now explain the method of laying down 
and constructing a propeller. Let us first take the 
case of a true screw. We will give the propeller 
four blades, and suppose its diameter to be 5 feet, 
and its pitch 10 feet. 

The first thing to be done, is to make the angle 



48 



THE CADET ENGINEER. 




of the blade. In Fig. 15, we lay off B C, equal to 

the circumfer- 
ence of the 
wheel, and A C, 
at right angles 
to B C, equal to 
the pitch. Then 
A B, represents 
the thread of 
the screw, and 
the angle B A 
C, is the angle required. 

Next, lay off C D, equal to the circumference of 
the hub, and D A C is the angle at the hub, (We 
suppose the hub to have a diameter of 12 inches at 
the ends, increased to fourteen inches in the centre. 
Its length is 12 inches). Now A D is the develop- 
ment of the helix described by one extremity of the 
generatrix, and A B, the development of the helix 
described by the other extremity. 

All the intermediate points of the generatrix will 
describe helices, whose developments will start from 
A., and run down to given points in D B, the develop- 
ment of the circumference. We will represent such 
helices as we shall use, at regular intervals of the 
circumference. Hence, divide the line D B into any 
number of equal parts, and draw lines from the points 
of division to the point A. These lines will be the 
development of the helices required. 

In this way we construct the developments of five 



THE SCREW PEOPELLER. 



49 



intermediate helices, A 1, A 2, etc. When we draw 
the plan of one of the blades, it w^ill be necessary to 
draw the helices undeveloped ; and w^e will show the 
manner of laying one down. In Fig. 16 we desire 
to construct the helix described by the outer ex- 
tremity of the generatrix. B C represents the pitch, 
10 feet, and the circle whose centre is A, the centre 
of the pitch, and whose diameter is D E, the diameter 
of the propeller, represents the circular distance 



^ Fi^.Jf}. 



B '■ 



V 1.-S 5 






travelled by the extreme point of the generatrix, 
while it passes over the axial distance, B C. So if 
we divide B C into any number of equal parts, and 
the circle into the same number, we can find points 
of the helix. Thus, when the extreme point of the 
generatrix has passed over the axial distance B F, it 
has gone in a circular direction, the distance D G, 
and hence the actual position of this point is H. 
Similarly, when the point has gone in an axial 



50 THE CADET ENGINEER. 

direction, the distance B D, and in a circular direction, 
the distance D G I, it will appear at K. 

Having found all the points, draw a curve through 
them, and this will be the helix described by the 
generatrix at the periphery. 

We might next draw the circle whose diameter 
equals that of the hub, and construct the helix 
described by the generatrix at the hub ; then divide 
the space between these circles into five equal parts, 
and construct the helices whose developments are 
A 1, A 2, etc. But it will be found that such parts 
of these helices as we shall use are practically straight 
lines, making angles with the line B C equal to 
1 A C, 2 A C, etc. This is equally true of the helices 
of the periphery and hub. So we can at once lay 
off these helices to construct the plan of the blades. 

In Fig. 17 draw the side elevation of the hub 
according to the measurements already given. Draw 
also the centre line A B. 

This has the same relative position as the line 
A C, Fig. 15, or B C, Fig. 16. Therefore, if from 
the centre of the hub we lay off lines making angles 
with A B, respectively equal to D A C, 1 A C, 2 
A C, etc., we shall represent the helices of which A D, 
A 1, A 2, etc., are the developments. 

We will next draw the side elevation of the blades. 
The helices will here appear as straight lines, parallel 
to the axis. They are indicated in the figure. We 
must determine how much the blades shall project 
beyond the ends of the hub. We will suppose that 



THE SCKEW PROPELLER. 



51 



they project 2 inches on the forward end, and 5 
inches on the after end. 




Having thus fixed^the limits of the blades, put in 
the side elevation to suit the fancy. This done, the 
form of the blade is fixed. Now observe the points 
where the boundaries of the side elevation cut the 
helices A B, A 5, A 4, etc., and project these points 
until they cut the corresponding helices laid down 
for the construction of the plan. Join the points so 
found by a curved line. 

It will be seen that the whole thickness of the 
blade at the periphery, and part of the thickness at 
the hub, are visible in the plan. Having put these 
in, the plan is complete. 



r^o 



THE CADET ENGIN"EER. 



Then find the points necessarj^ to construct the 

plan of the opposite blade, and draw as much of that 

as is visible. 

In the end elevation of the propeller all the helices 

will appear as circles. 

Draw the end elevation of the hub, and put in the 

helices, to correspond with those in the preceding 

views. Now project over points in the plan of the 

blade to corresponding helices in the end elevation. 

Connect these points by a curved line, and we have 

the end elevation of one blade. 

By transferring these points, we can construct the 

remaining blades. 

It now remains to find the development of one 

blade, and to show the thickness at various points. 

The helices that are represented as circles in the end 

elevation wdll evidently appear as ellipses in the 

development. The part 
E C D, for instance, will 
develop as an ellipse, the 
points E and D of which 
will be situated from the 
point C in a vertical direc- 
tion, the distance of their 
respective versed sines. So 
in Fig. 18 we transfer these 
points, D and E, at the 
proper vertical distances. 
The distance of these 

points from the centre line is shown in the plan, being 




G F{i.i8. 



THE SCREW PROPELLER. 



53 



the distance from the centre of the hub to where 
each of the points appears in the plan. 

For the points F and G, in the development, the 
same course is pursued. Find the versed sines of 
these points J then transfer them to the development, 
and take their distances from the centre line, as 
given in the plan. 

Having found all the points, connect them and 
thus complete the development. 

In Fig, 19, we have a section of the blade at the 
centre, showing the thickness, also a section taken 
near the edge of the blade. Now 
at any desired points of the de- 
velopment, draw lines perpen- 
dicular to the centre line ; lay off 
the centre and side thickness at 
these points, and connect them by 
curves, as indicated. The drawing 
of the propeller is then complete. 

The next case that we shall con- 
sider, is a propeller Avhose pitch 
expands from forward to after part 
of blade. 

In making the drawing of this propeller, we first 
draw the side elevation of the hub, and then show 
the side elevation of the blades. 

The previous method of drawing the helices to 
construct the plan will not answer. 

Suppose we wdsh to lay down a propeller whose 
diameter is 14 feet, and whose pitch expands from 




FU.19\ 



54 


THE 


CADET ENGINEER. 




20 to 


24 feet. In 


Fig. 20, make 


A B equal to 10 


feet, half the pitch 


at forward part 


. of blade 


, and A 


C equal to 12 feet, 


half the pitch 


at after 


part of 


blade. 


Theii from 


A, as a centre 


describe 


a circle, 




with a radius of 7 feet. Next construct the helices 
B D A and A E C, described by the extreme point 
of the generatrix, supposing it to have a pitch of 20 
feet, for the first half of its revolution, and a pitch 
of 24 feet for the other half. , 

But the pitch of the screw does not expand in this 
manner, but gradually commencing with a pitch of 
20 feet, and ending with a pitch of 24 feet. Hence, 
a curved line G A F drawn tangent to the two 
helices B D A and C E A, will represent the helix 
at the periphery. 

This operation must be repeated, with a circle 
whose diameter equals that of the hub, to find the 



THE SCREW PROPELLER. 00 

helix at the hub, and also, with circles drawn at 
regular intervals between the hub and periphery, to 
find the intermediate helices. 

When these are laid down, we can project the 
plan from the side elevation, as before shown, and 
the remaining operations are similar to those ex- 
plained in the case of the true screw. 

Now let us assume the screw that we desire to 
lay do^vn, to have a pitch expanding from hub to 
periphery. We will suppose its diameter to be 14 
feet, the diameter of the hub 2 feet, the pitch at the 
hub 15 feet, and at the periphery 21 feet. 

Now it is evident that the pitch will vary at 
every point in the circumference. But we suppose 
it to expand regularly, and hence, we have an in- 
crease of 6 feet in pitch, for an increase of 6 feet in 
radius. That is, the pitch is increased 1 foot for 
every foot from the hub. So, by the method pre- 
viously given, w^e can construct the helices of the 
periphery, hub and intermediate points, Avith their 
respective pitches. These helices are used to find 
the plan of the blade, the side and end elevations, 
and the development, being laid down as in the first 
case. 

Now that we have finished the drawing of the 
propeller, it only remains to show the parts needed 
for the pattern-maker and moulder. 

For the true screw, the only figures absolutely 
necessary, are the angle BAG, Fig. 15, the develop- 
ment and the thickness strips. The other views are 



56 



THE CADET ENGINEER 



useful, however, so that the mould may conform to 
the shape of the designed blade in minute particulars. 

In sweeping up a propeller, the angle is usually 
set several inches outside of the circumference of the 
wheel. This must be remembered in laying down 
the angle, which must be constructed for the distance 
from the centre of the hub, at which the angle is set. 
This distance should also be noted on the drawing, 
so that the moulder may know exactly where to 
place the angle. 

For the propeller with pitch expanding from for- 
ward to after part of blade, we must have an angle 
CAB, Fig. 21, where C E- A is a curved line drawn 
tangent to the two paths of the generatrix. 



J^,<i. Zi. 



"~-^. J^ 


I B ' C 



The manner of constructing this curve is as fol- 
lows : Let h C, represent the development of the 
circumference where the angle is set h a and h d^ the 
two pitches. The generatrix, however, does not 



THE SCKEW PKOPELLEE. O^ 

describe a whole circumference, but only the portion 
B C, so that B A and B D are the fractions of the 
two pitches. That is, the developed path of the 
generatrix at its commencement is C D, and at its 
termination C A. Hence, C E A drawn tangent to 
the terminal paths of the generatrix, is the path 
required, and C A B is the angle of the screw. 

In sweeping up a blade, the after part must always 
be down. This should be remembered in construct- 
ing the angle. 

For a propeller with pitch expanding from hub to 
periphery, two angles must be used as guide for the 
sweep; one, the angle at the periphery, and the 
other, the angle at the hub. 

For cast-iron propellers, a good proportion of metal 
is 1 by weight, Scotch pig, and the remainder scrap 
and American pig-iron. 

For a composition propeller, a good mixture is as 
follows : 

88 Copper ^ 

10 Zinc y by weight. 
2 Tin J 

There are many rules for finding the area of pro- 
peller blades, but they are, as a general thing, only 
applicable in the case of a true screw, where no sur- 
face is cut away from the hub, or added at the 
periphery. The designs of blades are so varied, that 
these rules do not give very accurate results. A 
close approximation to the area of a blade, of what- 
ever form, may be obtained from the development. 



58 THE CADET ENGINEER. 

Suppose (Fig. 22) we desire to find the area con- 
tained between the curve A B C D E F G, the line 
H S, and the perpendiculars H A and S G. Divide 
the line H S into any even number of equal parts. 




and erect perpendiculars I B, K C, etc., at every point 
of division. Measure each of these perpendiculars, 
and number them, commencing at the left hand. 
Thus H A designate No. 1, I B No. 2, K C No. 3, 
and so on. Then the area required is found by 
taking the sum of the extreme perpendiculars H A 
and S G, adding to this four times each of the even 
numbered perpendiculars, as I B, L D, and F P, 
also twice each of the odd numbered perpendiculars, 
as K C and E; and multiplying this whole sum 
by J of the distance between two perpendiculars, 
as H I. 

Example. — In the figure under consideration, let 
us divide the distance li S into six equal parts, each 
of which is one foot in length, and erect perpendicu- 
lars at the points of division. Let us also have the 
lengths of the perpendiculars given as follows : 

H A = No. 1 = 1 feet. I B = No. 2 = 3.5 feet. 



THE SCKEW PKOPELLEK. 59 

K C = No. 3 = 3.3 feet. L D = No. 4 =: 3.7 feet. 

E = No. 5 = 4.3 feet. P F = No. 6 = 5 feet. 

S G = No. 7 = 6 feet. 

Then, by the rule, the area HABCDEFGSis 
(1 of HI)X(HA + S G + 4XIB + 2XKC + 4 
XLD + 2XEO + 4XPF)=: 

(lofl)X (4 + 6 + 4X3.5 + 2X3.3 + 4X3.7 + 
2 X 4.3 + 4 X 5) = 24.66 square feet. 

This rule can be applied to the development of a 
blade of a propeller, as Fig. 18. 

The centre line must be divided into an even 
number of equal parts, and then the area between 
this centre line and each half of the development 
can be calculated, as sho^vn above. The sum of the 
two areas is the helicoidal surface of one blade. 
Multiply this by the number of blades, and we have 
the wdiole helicoidal surface of the propeller. 

To find the acting surface of the propeller, we 
have only to compute the area of the end elevation 
of a blade (Fig. 17), and multiply it by the number 
of blades. 

Propellers were formerly cast in flask moulds from 
patterns. But of late years this method has been 
seldom employed, and loam moulding has been 
usually practised. The process of sweeping up and 
moulding a propeller in loam is so interesting, that 
this article would be incomplete without some men- 
tion of it. We will, therefore, attempt a brief 
description of the mode of operation. 

The pattern-maker first constructs an angle (Fig. 



80 



THE CADET ENGINEER. 



rM2^ 



23) J as a guide for the sweep. This angle is, of 
course, tl}£ angle of the screw undeveloped, and there- 
fore its base is circular. It is con- 
structed from the developed angle in 
the drawing sent to the shop, by trans- 
ferring the perpendicular distance be- 
tween the base and hypothenuse at 
various points. In casting large screws, 
the hypothenuse of the angle is usually 
faced with a strip of iron, to prevent 
wear. In Fig. 19 we have given the 
thickness of the blade on a line pass- 
ing through the centre of the hub, per- 




pendicular to the axis; and in Fig. 18 we have the 
thickness of the blade, taken at various points of 
this line, on lines perpendicular to it. Thickness 
strips are made, corresponding to these sections, the 
strips perpendicular to the centre strip, being made 
in two pieces, divided at the centre line. These 
strips are generally of inch or inch and a quarter 
stuff. The sweep and the hub complete the articles 
provided by the pattern-maker ; and when the hub 
is very large, this is also swept up. 

The moulder provides a plate. A, Fig. 24, of from 
10 to 20 inches greater diameter than that of the 
propeller. A rod C is secured at right angles to the 
plane of this plate, and serves as a spindle for the 
sweep. A level bed is first svfept up upon the plate, 
with a slight depression at the periphery, just the 
width of the base of the angle, and a cylindrical 



THE SCREW PROPELLER. 61 

elevation in the centre, upon which the hub is placed. 
When this bed is perfectly dry, the hub D is put in 
its place, and the sweep B is secured to the spindle. 
The angle E is also placed at the periphery of the 



3il^^HllllKH 

^^A^kai^HiHB^Hiiuiiiuuiuiiiiiii.inns^H 



bed. Now, it is evident that if the sweep revolves 
around the spindle, advancing at the same time in 
an axial direction (as it must do, from the fact of 
its contact with the face of the angle), its lower 
edge will be the generatrix of a screw. So a bed of 
loam and brick is built upon the plate, and by the 
aid of the sweep, its face is made to coincide with 
the flat face of one blade of the propeller. This 
operation must be repeated, to sweep up the other 
blades. Let F represent the face of one of the beds 
that has been swept up. It is covered with a coat 
of parting sand, and then we are ready to mould the 
blade. The line passing through the centre of the 
hub, perpendicular to the axis, is drawn on this face 
by means of a spirit-level. The centre thickness 
strip is then put on the face along this line, and 



62 ^ THE CADET ENGINEER. 

secured lightly by nails, and the other strips are also 
secured in their proper places. When this is done, 
it is easy to mark the outline, G, of the blade. The 
moulder then fills in the spaces between the strips 
with sand, and with the aid of the strips readily 
gives it the shape of the blade. The strips are then 
removed, and the spaces previously occupied by them 
are filled with sand; so that we have a complete 
mould of the blade. It only remains to construct 
the cope. A layer of sand and loam is put over the 
face and mould of the blade, and the cope is built 
over the face of bricks and loam, strengthened at 
short intervals by iron plates and rods. An iron 
plate forms the top of the cope, and there are lugs 
on this and on the bottom plate, so that the mould 
and cope can be finally connected by bolts. When 
the cope is completed, it is lifted off, and the mould 
of the blade is removed from the face. We then 
have the shape of the blade accurately preserved in 
the cope. When all the blades have been similarly 
formed, the moulder removes the hub, and introduces 
the core. Where a hub has been swept up, and 
constructed of bricks and loam, it can be easily 
broken to pieces and removed. When it is made of 
wood, and cannot readily be drawn, it is removed, a 
piece at a time, or there are partings in the beds 
upon which the blades are moulded, so that these 
beds may be partially removed, and replaced when 
the hub is taken out. This completes the mould, 
at least so far as there is anything novel in its con- 



COMBUSTION OF COAL. 68 

struction. Of course, provision must be made for 
vent ; the mould must be dried, and buried in a pit, 
before casting the propeller. 

§ 6. Comhustion of Coal. 

Combustion is merely the combination of any 
substance with oxygen, by which union heat is 
developed. In the combustion of coal, carbon is the 
principal substance that unites with oxygen, and 
the air is the source from which the oxygen is 
derived. In 100 pounds of average anthracite coal 
the principal constituents are : 

88 pounds. Carbon. 
3 pounds. Hydrogen. 
1 pound. Nitrogen. 
1 pound. Oxygen. 
7 pounds, solid refuse, or ashes. 

On the application of heat to the coal, a gas is 
evolved consisting of two atoms of hydrogen and 
one of carbon. If air is now admitted to the gas, 
the hydrogen unites with an atom of oxygen and 
passes off* as steam, while the carbon uniting with 
two atoms of oxygen forms carbonic acid. Thus we 
need four atoms of oxygen for the perfect combustion 
of this gas. Atmospheric air consists mainly of 
oxygen and nitrogen, an atom of oxygen to every 
two atoms of nitrogen, or, as the volume of an atom 



6i THE CADET ENGINEER. 

of nitrogen is twice that of an atom of oxygen, we 
say that atmospheric air contains 20 per cent, of 
oxygen and 80 per cent, of nitrogen, with regard to 
volume. An atom of nitrogen weighs 1| times as 
much as an atom of oxygen ; so that the constituents 
of air are in the proportion, by weight, of 1 pound 
of oxygen to 3^ of nitrogen. So for every volume 
of oxygen that is required in a furnace, five volumes 
of air must be admitted. 

After the combustion of the hydrogen in the coal 
is effected, that of the carbon commences, and this 
is, in fact, the main substance, which we desire to 
consume as perfectly as possible. In a furnace, 
carbon unites with oxygen in two proportions, form- 
ing carbonic acid and carbonic oxide. There is 
another compound of carbon and oxygen, but that 
is not formed in the combustion of coal. 

Carbonic acid is a gas consisting of one atom of 
carbon and two of oxygen. As the relative weight 
of an atom of carbon, referred to hydrogen as a 
standard, is 6, and of oxygen 8, the weight of one 
atom of carbonic acid is 22. Its volume is the same 
as that of an atom of hydrogen, or 1. 

Carbonic oxide is also a gas consisting of one atom 
of carbon and one of oxygen, having, therefore, an 
atomic weight of 14. Its volume, however, is the 
same as that of carbonic acid. 

Oxygen unites directly with carbon to form car- 
bonic acid, which is the result of perfect combustion. 



COMBUSTION OF COAL. 6d 

But if carbonic oxide is one of the products of com- 
bustion, it is evident that heat is lost ; for carbonic 
oxide is convertible into carbonic acid by the addi- 
tion of another atom of oxygen, and heat is the 
result of the union. As carbonic acid is the result 
of the union of oxygen and carbon in the furnace, 
we must explain how it is that carbonic oxide can 
form one of the products of combustion. If air enters 
the ash pits and oxygen unites with the carbon, car- 
bonic acid is formed ; but this gas passing up through 
the coal, may unite with another atom of carbon 
and form carbonic oxide, so that the carbon will pass 
away half consumed. Now, if we can supply this 
carbonic oxide with another atom of oxygen, car- 
bonic acid will again be formed, and the combustion 
is complete. For this reason air is sometimes 
admitted through the furnace doors above the fire. 

While discussing the subject of combustion, we 
must speak of the plans of using water for fuel. 
Water, which was formerly supposed to be an ele- 
ment, is composed of hydrogen and oxygen, one 
atom of each, or by volume, two parts of hydrogen 
to one of oxygen, and by weight, one part of hydrogen 
to eight of oxygen. Now, as the combustion of 
hydrogen produces intense heat, it was thought that 
water could be decomposed and the hydrogen con- 
sumed to great advantage. Water can readily be 
decomposed by contact with carbon, at a high tem- 
perature ; so it was proposed to admit water in the 



^6 THE CADET ENGII^EER. 

form of superheated steam, to charcoal or coke, at a 
temperature of about 1800°. Then, the water being 
decomposed, the oxygen would unite with the carbon 
and form carbonic acid, while the hydrogen set free, 
if ignited in the air, would again become water and 
develope much heat in the process. This is a very 
plausible theory, except for the impossibility of 
creating force. Experiment and reason both confirm 
the fact, that the heat required to decompose the 
water is just as great as that produced by the subse- 
quent combustion of its constituents. All schemes 
for producing additional heat by the use of water as 
fuel, may be classed among perpetual motions. Prac- 
tically, we lose all the heat required to raise the 
water into steam, before it is admitted to the furnace. 
The draft in a chimney or smoke-pipe is caused 
by the difference of pressure betw^een the heated air 
within and the atmosphere without. Hence, the 
higher we make a chimney, the greater will be the 
draft. Also, cylindrical chimneys are the best, as 
there is less friction of the heated air and gases. 
Theoretically, the area of a chimney should be 
greater than the area for the admission of air to the 
furnaces, on account of the chimney expelling this 
air, and also the products of combustion. Let us 
determine the relation. In doing this, the table 
given below will be found serviceable. 



COMBUSTION OF COAL. 



67 



Substance. 


Atomic Weights. 


Volumes. 


Hydrogen .... 
Carbon .... 


1 
6 


1. 
.5 


Oxygen .... 
Nitrogen .... 
Watery Yapor ... 
Carbonic Acid 


8 
U 

9 
22 


.5 
1. 

.14 
1. 


Air 


36 


2.5 


Carbonic Oxide . 


14 


1. 



As the atomic weight of hydrogen is 1, and of 
carbon 6. in anthracite coal we shall have 3 atoms 
of hydrogen for every 88-^6 z= 14.66 atoms of carbon. 
We will neglect the other constituents, as they would 
not affect the result materially. Now, to effect the 
perfect combustion of this carbon, we must have 
14.66X2 = 29.32 atoms of oxygen, and for the 
hydrogen 3 atoms, or 32.32 atoms of oxygen in all. 
With this oxygen, 32.32 X 2 =z 64.64 atoms of 
nitrogen must be admitted. The volume of this 
64.64 atoms of nitrogen is 64.64, and of the 32.32 
atoms of oxygen 32.32-r-2zzl6.16, so that the total 
volume of the air admitted to the furnace is 64.64 
+ 16.16 = 80.8. Now let us look at the volumes 
of the products of combustion, and then we shall 
have the whole volume passed through the smoke- 
pipe. The volume of the carbonic acid formed from 
the 14.66 atoms of carbon, and the 29.32 atoms of 
oxygen, is 14.66. The nitrogen in the air that con- 
tains this oxygen is 29.32 X 2 = 58.64 atoms, and 



68 THE CADET ENGINEER. 

its volume is 58.64. The volume of the three atoms 
of water, formed by the union of the three atoms of 
hydrogen with three atoms of oxygen, is .14 X 3 =i 
.42. The nitrogen passing through with this oxygen 
is 3X2 = 6 atoms, and its volume is 6. So we 
have, for the volumes passing through the smoke- 
pipe : 



14.66 volumes, carbonic acid. 


58.64 


" nitrogen. 


.42 
6. 


'' watery vapor. 
'' nitrogen. 


79.72 


volumes. 



By this, as the relation between the air admitted 
to the furnace, and the products of combustion, is as 
80.8 to 79.72, it would seem that the areas should 
be about equal. But gases expand about -^ of their 
volume for every degree of heat Fahrenheit that they 
receive. Let us suppose that the air entering the 
furnace has a temperature of 100°, and that the 
products of combustion have a temperature of 250°. 
Their volume will then be increased 150-^491=:: 
.3055. Hence the volume of the products of com- 
bustion is 79.72 + (79.72 X .3055) zz 103.05, and the 
relation between the areas for admitting air and dis- 
charging the gases is as 80.8 to 103.05. But no 
furnaces are so well constructed as to absorb all the 
oxygen from the air passing through them. Indeed, 
it is estimated that about I of the oxygen passes off 



ERECTION" OF ENGINES. 69 

uncombined. So it may be well to allow 25 or 30 
per cent, more space for the admission of air to a 
furnace than is barely required for perfect combustion. 
If the combustion is incomplete, we form carbonic 
oxide, which has the same volume as carbonic acid, 
but only develops half the heat. 

§ 7. Erection of Engines. 

As the contracts for the hull and machinery of 
steam vessels are at present issued to the shipbuilder 
and engineer simultaneously, the engineer is thereby 
granted a sufficient time to have the work prepared 
and temporarily erected before the ship is ready to 
receive it. The shipbuilder generally adjusts the 
dead wood for the propeller shaft, and sets it in a 
parallel line with the load line, and the centre fore 
and aft line of the ship. 

With all marine engines, whether propeller or side- 
wheel, the constructing engineer takes the fore and 
aft (centre line) as the base of his work longitudi- 
nally, and the level of the deck beams as the base 
transversely or athwartship. From the deck (in 
propellers) the fore and aft (centre) line is trans- 
ferred at the midship section to the centre of the 
stern-post. The point of contact with a perpen- 
dicular line from deck will, when parallel with the 
load line, give the main shaft line. This is the base 
from which all others are obtained, as all the motions 
of the engines are either parallel or perpendicular 



70 THE CADET ENGINEER. 

thereto. Athwartship the work is levelled by the 
deck beams (lower side), and made parallel to them, 
as it is from the deck that the ship is levelled or 
trimmed. ' 

It is customary for the constructing engineer to 
furnish plans of the height and size of the cross 
keelsons, etc., used for the foundation of the engines. 
When the hull has sufficiently advanced to allow the 
engineer to proceed with the erection of the engines 
on board, the form of the base of bedplate is trans- 
ferred by means of a template. The centre line of 
shaft is marked thereon, also diagonal points, by 
which the centre line is governed from distortion, 
placed in proper position and marked off on board, 
using the main shaft line fore and aft, and a line 
parallel with the level of deck beams athwartships, 
to determine the plane of the base. The foundations 
are then pricked oif at the proper heights (making 
due allowance for screwing down the foundation 
keelsons), and the bolt holes marked off, ready for 
the borers, by which means everything is prepared 
to receive the bedplates, etc. In placing a side-wheel 
engine on board a vessel (a beam engine, for instance), 
care should be taken to obtain the fore and aft centre 
line accurately, as it is the most important, and the 
one from which all others are derived. 

It is obtained thus : get the mean centre from out- 
side to outside of planking on deck, and draw it fore 
and aft on the centre of the deck. Then get the 
athwartship line at right angles with the fore and 



• ERECTIOX OF EXGIXES. 71 

aft line, and level with the deck beams. To set the 
engine keelsons, transfer the fore and aft centre line 
to the main keelson, at right angles with the ath wart- 
ship or main shaft line, and draw the line out of 
winding (by sight) with the fore and aft line. Then 
adjust the engine keelsons equidistant and parallel 
thereto. Level off the keelsons, so that the face for 
condenser will be at right angles with the above per- 
pendicular line. Set the channel way so that the 
centre of the condenser will coincide with the fore 
and aft centre line. Erect the gallows frame, and 
adjust it in conformity to a line drawn from the 
lower fore and aft centre line, at right angles with 
the main shaft hne, and proceed throughout with 
parallels and perpendiculars. 

The boiler foundation keelsons are laid at a line 
so as to make the lower face of the boilers, and the 
line of the tubes, parallel with the load hne fore and 
aft, and the deck beams athwartship. Care should 
be taken, for the preservation of the boilers, that 
oak is not used in contact with the iron, as a strong 
acid is generated therefrom, which is a powerful and 
rapid oxidizer, and will soon destroy the iron. Yellow 
pine is far preferable for foundations. 

As the bases of boilers are very irregular, it is 
impossible to lay the foundations accurately, there- 
fore a putty is generally used (made of whiting and 
linseed oil) to fill up the irregularities. Boilers are 
generally secured by braces, firmly bolted to the hull, 
to prevent them from becoming displaced by any 



72 THE CADET ENGINEEE. 

motion or strain. In ocean steamers it is advisable 
(if practicable) to place the boilers at the centre of 
gravity (fore and aft), and to have the coal bunkers 
extending equal distances from the same, with the 
entrance in the centre, so that the engineer may alter 
the trim of the vessel at pleasure, and keep her on 
the best running line. Care should also be taken by 
the designers to proportion the weight on each side 
of the keelson, to keep the ship in trim (athwart- 
ship) ; also to have the coal bunkers on each side of 
equal capacity, and equidistant from the centre. 

All holes bored through the sides of ships for 
deliveries, blow^-pipes, and sea cocks, should be first 
lined with lead, and then bushed with copper, to 
prevent the destruction of the timber, also to prevent 
leaks. The dead wood for a propeller shaft should 
first be accurately bored out with a boring bar, and 
then lined with lead pipe, through which dies should 
be drawn to make it lie close to the wood, and pre- 
vent leakage. It should then be lined with copper 
pipe, through which dies should also be drawn, to 
render it perfect. Brass boxes with lignum vitae 
bearings, for a shaft cased with composition, should 
then be fitted in in segments and bolted on, so that 
when worn out, they can be replaced without injury 
to the dead wood, lining, etc. 

Bust joints, composed of sal ammoniac, iron borings, 
and water were formerly employed for all the perma- 
nent joints around engines, such as where the steam- 
chest joins the ports of a cylinder, and the like. 



STEAM. 73 

Thev are out of use noW; however, and faced joints 
take their place. 

§ 8. Steam. 

Steam, according to Dr. Lardner, is air made from 
water. It may be defined as the gaseous condition 
of water, and is formed when water boils. It is an 
elastic fluid, and when not in contact with water, 
follows the same laws as other non-permanent gases. 
That is, it expands about ^ of its volume for everv 
degree of heat Fahrenheit that it receives, and the 
elastic force remains unaltered ; but as long as the 
temperature is constant, the elastic force varies in- 
versely as the volume. 

Steam in contact with water contains moisture, 
and is termed saturated or common steam. When 
separated from the water, and heated to a higher 
temperature than is due to its pressure, it is termed 
surcharged or superheated steam. Now let us observe 
the process of the formation of steam. Let us take 
a vessel containing water at the temperature of 32°, 
and apply heat to it, say from the flame of a spirit 
lamp. We will observe the time occupied in raising 
the temperature of the water to 212°, supposing the 
heat applied to be constant. For the sake of illus- 
tration, let us take this time as one hour. 

When the water assutiies the temperature of 212°, 
if the vessel is uncovered, and the barometer stands 
at 29.9, it will get no hotter, but steam will com- 
mence to escape, and the water will boil. If now 



74 THE CADET ENGINEER. 

the time be noted, from the moment the water 
assumed the temperature of 212° until all the water 
is evaporated, it will be found to be 5 J hours. 

If all the steam were preserved in a receiver, it 
would be found to have a temperature of 212°, a 
volume 1696 times greater than the water from which 
it was generated, and a pressure of 14.7 pounds to 
the square inch. 

Now, as it requires 180° of heat to raise the tem- 
perature of the water from 32° to 212°, and 180 X 
5 J, or 990°, to convert that water into steam, which 
continued to have a temperature of 212°, we say 
that the 990° of heat are latent. This gives us 212° 
+ 990°, or 1202°, as the total heat of steam gener- 
ated in an open vessel, when the barometer stands 
at 29.9, or the pressure of the atmosphere is 14.7 
pounds to the square inch. 

The preceding demonstration has given the results 
in round numbers. The precise latent heat of steam, 
whose sensible heat is 212°, as determined by Reg- 
nault, is 966°.66. 

When the pressure under which steam is gener- 
ated is increased, the sensible heat is also increased, 
and the total heat (or the sum of the latent and 
sensible heat) is also increased. The volume of the 
steam diminishes as the pressure increases. 

Table I. gives the temperatures and volumes of 
steam at different pressures. 



EXPANSION OF STEAM. 



75 



TABLE I. 



Pounds 


Elastic 


Force in 


Temperature 






per 

Square 

Inch. 


Inches of 


Atmo- 


Fahrenheit 


Volume. 


Total 

TT i 


Mercury. 


sphere. 


Degrees. 




Meat. 


1 


2.04 


.068 


103. 


20958 


1145.35 


6 


10.20 


.340 


163.065 


4769 


1163.61 


10 


20.40 


.680 


193.165 


2435 


1172.77 


15 


30.60 


1.020 


212.8 


1169 


1178.84 


20 


40.80 


1.360 


228.5 


1281 


1183.55 


25 


51. 


1.7 


241. 


1044 


1187.38 


30 


61.2 


2.04 


251.6 


883 


1190.66 


35 


71.4 


2.380 


260.9 


767 


1193.45 


40 


81.6 


2.72 


269.1 


679 


1195.84 


45 


91.8 


3.06 


276.4 


610 


1198.22 


50 


102. 


3.4 


283.2 


554 


1200.21 


60 


122.4 


4.080 


295.6 


470 


1204.06 


to 


142.8 


4.76 


306.4 


408 


1207.32 


80 


163.22 


5.440 


315.8 


362 


1210.23 


90 


183.62 


6.12 


324.3 


325 


1212.83 


100 


204. 


6.8 


332. 


295 


1215.14 


110 


224.4 


7.48 


339.2 


271 


1217.31 


120 


246.8 


8.16 


345.8 


251 


1219.36 


130 


265.2 


8.84 


352.1 


233 


1221.31 


140 


285.6 


9.52 


357.9 


218 


1223.09 


150 


306. 


10.2 


363.4 


205 


1224.76 



§ 9. Expansion of Steam. 

If we stop admitting steam to the cylinder before 
the piston has arrived at the end of its stroke, the 
steam already admitted v^ill expand, and cause the 
piston to complete its stroke. Theoretically, this 
steam will expand according to Mariotte's law, or its 
pressure will be inversely proportional to the space 



'6 



THE CADET ENGINEEE. 



it occupies. Practically, there are many things to 
affect this law. 

The question of expansion is now on its trial. So 
in this article we will only treat the subject theo- 
retically. 

The theoretical curve of expansion is an hyper- 
bola of which A X and A Y, Fig. 25, are the asymp- 
totes, or lines which the curve cuts at an infinite 
distance. 

Now the rectangle A B G m, represents the 
mechanical effect of the steam before expansion, and 
the area C V D E m, represents the mechanical effect 
during expansion. We call the area A B C m, unity, 
and we will find 
the area C Y D E 
m, by means of 
Naperian Loga- 
rithms. These 
have the number 
2.7182818, for a 
base, and the Na- 
perian logarithm 
of any number 
may be found 
from the common logarithm by multiplying the latter 
by 2.30258509. They are frequently called hyper- 
bolic logarithms, because the numbers express the 
areas between the asymptotes and curve of the 
hyperbola, these areas being limited by ordinates 
parallel to the asymptotes. But such areas may be 




EXPANSION OF STEAM. 77 

made to denote any system of logarithms whatever. 
In the case of the hyperboUc logarithms, however, 
the asymptotes are at right angles to each other, and 
hence we see that the Naperian, or hyperbolic loga- 
rithm of the asymptote will give us the area required. 
Now the asymptote of the hyperbola in question is 
?i X -^ m zz 71, where n represents the number of 
times the line A m, which is unity, is contained 
in A E. 

Hence, in order to find the mechanical effect of 
the steam during expansion, we have only to divide 
the space passed over by the piston before expansion, 
(which we call unity), by the number of such spaces 
in the whole length of the cylinder (which we call 
n), and take the Naperian logarithm of the reciprocal 
of this fraction. Adding the work performed before 
expansion, we have the total mechanical effect of 
the steam during one stroke. 

But the mechanical effect is equal to the mean 
pressure, multiplied by the distance over which it is 
exerted. So we can obtain the mean pressure by 
multiplying the mechanical effect by the initial pres- 
sure of steam, and dividing by n, the distance through 
which the force of the steam is exerted. 

The pressure at the end of the stroke will evi- 
dently be obtained by dividing the initial pressure 
by n. 

The per cent, of gain by expansion will be obtained 
by multiplying the mechanical effect during expansion 
by 100. 



78 



THE CADET ENGINEER. 



Example. — Suppose we have steam of 20 pounds 
pressure, and cut oif at i stroke. 

Our fraction here is i, and nz=z4c. 

Hyp. log. 4 =1 1.386 := mechanical effect during 
expansion; and 1.386 + lzz2.386z=: total mechanical 
effect. 

(2.386 X 20) -^ 4 1= 11.93 = mean pressure. 

20-^-4 = 5 = pressure at end of stroke. 

1.386 X 100 = 138.6 = per cent, of gain by cutting 
off. 

Table II. gives the hyperbolic logarithms that are 
needed for calculations at different points of cutting 
off 

TABLE II. 



Number. 


Hyp. Logarithms. 


Point of 


Cutting. 


1.143 


.133 


1 stroke. 


1.333 


.28t 


1 




1.6 


A1 


|. 




2. 


.693 


i 




2.666 


.982 


1 




4. 


1.386 


4 




8. 


2.079 


i 





A very convenient way of laying off the theo- 
retical curve of expansion, so as to find the pressure 
at any point of the stroke, is shown in Fig. 26. 

Draw a section of a cylinder, A B C D, of the 
required diameter and stroke. Divide the diameter 
A B into any even number of equal parts, and through 



EXPAXSIOX OF STEAM. 



Fi'j.U: 



my" 



n M ihs. 



the points of division draw lines perpendicular to 
A B. Produce the Hne B A, and make A P equal 
to half of B A ; also divide A P into equal parts of 
the same size 
as those into 
which we di- 
vided A B. 
Then draw P 
perpendicular 
to AB. 

Now suppose 
the steam is 
cut off at E, 
and expands 
through the 
remainder of 
the stroke. 
Draw a line 
from E through 
G, the middle 
point of A B^ 
and note the 
point when it cuts the line P 0. From draw a 
line through the point of division on A B, next to 
the left of G, and note where it cuts the perpendicular 
drawn through the first point of division of the line 
B A. This is a point of the required curve. Then 
from draw a line through the second point of 
division to the left of G, and note where it cuts the 
second perpendicular. This is also a point in the 



i 



80 THE CADET ENGINEER. 

curve of expansion. Continue this operation until 
all the points are found, and then describe through 
them the curve E H I. 

Next lay off a line E S equal to the diameter of 
the cylinder, and divide it into as many equal parts 
as there are pounds in the initial pressure of the 
steam. This is our scale, and by applying it at any 
point of the stroke, the pressure of steam is indi- 
cated. 

In the figure under consideration the number of 
divisions in A B corresponds with the number in 
K S, so that the pressure at any point of the stroke 
can be at once read off. 

Before leaving the subject of expansion, we will 
take into consideration the gain in fuel derived by 
cutting off. 

When we know the point of cutting off, and, con- 
sequently, what fraction of a cylinder full of steam 
is used, we can at once ascertain the per cent, of 
gain in fuel. We can also ascertain the mechanical 
effect of the steam. Now this mechanical effect will, 
of course, be less than it would be if the steam were 
not cut off. 

We ascertain the difference between the mechanical 
effect at full stroke and the effect when the steam is 
cut off at a certain point, and then proceed to find 
the per cent, of fuel required to make the latter 
mechanical effect equal to the former. This we do 
by making a proportion, as follows : 

TTw mechanical effect wJwn the steam is cut off at a 



EXPANSION OF STEAM. 81 

certain point : the difference hetiveen the mechanical 
effects of steam following full stroke, and steam cut off 
at the given -^int of strohe : : the 'per cent, of fuel used 
when the steam is cut off at a given point : the per cent, 
of fuel required to make up the difference in mechanical 
effects. 

This latter quantity must then be subtracted from 
the per cent, of fuel gained by cutting off at the 
given point, and the remainder is the per cent, of 
gain in fuel derived by cutting oflfj wiien the same 
effect is produced as if the steam followed full stroke. 

Examples. — 1. What is the per cent, of gain iii^ 
fuel, if the steam is cut off at half stroke, and made 
to produce the same effect as if it followed full 
stroke ? 

By Table II. the mechanical effect, if the steam 
were cut off at half stroke, would be 1.693, and as 
only half a cylinder full of steam would be used, the 
saving in fuel would be 50 per cent. ; so that only 
50 per cent, of fuel would be used. But if the steam 
followed full stroke, the mechanical effect would 
be 2. 

2 — 1.693 =: .307 = difference in mechanical effects. 
Now to find the per cent, of fuel required to make 
up this difference, we make the proportion : 

1.693 : .307 : : 50 : 9. 
So that 9 per cent, more fuel must be expended to 
produce the same mechanical effect, cutting at half 
stroke, as if the steam followed full stroke. Hence, 



82 THE CADET ENGINEER. 

50 — 9 1=41 per cent, gain in fuel, cutting off at 
half stroke. 

2. What is the per cent, of gain in fuel, fufilling 
the same conditions as in example Ist, except that 
the steam is cut off at quarter stroke ? 

2.386 =: mechanical effect, cutting off at quarter 
stroke. 

75 per cent, n gain in fuel, cutting off at quarter 
stroke. 

4 zz mechanical effect, following full stroke. 

25 = per cent, of fuel used, cutting off at quarter 
stroke. 

4 — 2.386i=1.614zzdifference in mechanical effects. 

2.386 : 1.614 : : 25 : 16.8. 

16.8 zz per cent, of fuel required to make up the 
difference in mechanical effects. 

75 — 16.8n58.2 iziper cent, of gain in fuel derived 
from cutting off at quarter stroke, the steam pro- 
ducing the same mechanical effect, as if it followed 
full stroke. 

Now, it is evident that to make the mechanical 
effect of the steam, when it is cut off, equal to the 
effect when the steam follows full stroke, the initial 
pressure must be increased, so as to make the mean 
pressure the same in both cases. 

Suppose that, when we follow full stroke, the mean 
pressure of the steam is a given number of pounds y 
it is required tp find the initial pressure of the steam 
that is cut off at a certain point, which in expanding 



EXPAXSIOX OF STEAM. 83 

will have the same mean pressure as in the first case. 
This is a problem which may be stated as follows : 

Required to find a number, which, multiplied by 
the mechanical efiect of the steam that is cut off, 
and divided by the distance over which this mechani- 
cal effect is exerted (this result being the mean 
pressure of the expanded steam), shall equal the 
mean pressure when the steam follows full stroke. 

To find this number, we have only to make a pro- 
portion, thus : 

The mechanical effect of tlie steam that is cut off : the 
number of times the steam is expanded, or the distance 
over which the mechanical effect is exerted : : tJw mean 
pressure folloiving full strolce : tlie mean pressure re- 
quired. 

Examples. — In the two preceding examples, sup- 
pose the pressure of the steam when following full 
stroke to be 20 pounds : required to find the initial 
pressure of the steam that is cut off. 

1st. When the steam is cut off at half stroke : 
Here, 1.693 =: mechanical effect. 

2 zz number of times the steam is expanded. 
Hence, 1.693 : 2 : : 20 : 24.09. 

So that 24.09 is the initial pressure when the 
steam is cut off at half stroke, which will produce 
the same mechanical effect as steam of 20 pounds 
pressure following full stroke. 

2nd. When the steam is cut off at quarter stroke : 
2.386 zz mechanical effect. 
4 zz number of times the steam is expanded. 



84: 



THE CADET ENGINEEK. 



Then, 2.386 : 4 : : 20 : 33.5. 

So that 33.5 pounds is the required initial pressure 
of steam. 

It must be remembered, that though the initial 
pressure of the steam is greater when cutting off, to 
produce the same mechanical effect as when follow- 
ing full stroke, the gain in fuel is effected from the 
fact, that in the first case, only half a cylinder full 
of steam is used, and in the second, only a quarter. 
Table III. gives the gain in fuel, derived by cutting 
off at various points ; also the relation between the 
initial pressure of steam when cutting off and follow- 



ing full stroke. 



TABLE III 



Point of 


Per Cent, of 
Gain in Fuel. 


Initial Pressure Kequired. 


Cutting Off. 


Following Full Stroke. 


Cutting Off. 


J stroke 


11. t3 




1.008 


3 " 


22.4 




1.03 


8 " 


32. 




1.09 


"2 


41. 




1.18 




49.6 




1.32 




58.2 




1.67 


1 " 


6T.6 


^ 


2.6 



When the pressure of steam following full stroke 
is given, the initial pressure of the steam that is cut 
off, can be found by multiplying the number in the 
last column, by the pressure of the steam that fol- 
lows full stroke. 

It must be remembered that all the results given 



EXPANSION OF STEAM. 85 

in the preceding article are theoretical. They must 
not be confounded with the gains in actual practice. 
Back pressure is a constant prejudicial resistance, 
caused in the case of a condensing engine, by the 
impossibility of obtaining a perfect vacuum in tbe 
condenser; and in a high pressure engine, by the 
pressure of the atmosphere and resistance offered to 
the exhausting of the steam by friction and tortuous 
passages. This back pressure and tbe friction of 
the engine, interpose a limit even to theoretical 
expansion. For the effective pressure at the end of 
the stroke, which is the difference between the actual 
pressure at the end of the stroke, and the back pres- 
sure, must be at least equal to the pressure per 
square inch required to overcome friction. So, if we 
know the initial pressure of steam, the length of 
stroke and the required terminal pressure, we can 
find the point of cutting off by the relation between 
the volume and pressure of steam. 

Example. — Suppose the initial pressure of the 
steam is 20 pounds above a perfect vacuum; that 
the stroke is 4 feet; that the back pressure is 3 
pounds per square inch, and the pressure necessary 
to overcome friction, 2 pounds per square inch. 
What is the shortest point of stroke at which the 
steam can be cut off? 

3 + 2 = 5 pounds, a constant resistance. So that 
the least terminal pressure of the steam is 5 pounds. 

Now as the initial pressure of the steam is 20 



86 THE CADET EXGIXEER. 

pounds, if it is expanded to 5 pounds, its volume 
must be 

20-^5 = 4. 

So that tlie steam is cut off at quarter stroke, or, 
as the stroke is 4 feet, at 1 foot from commencement. 

The following example will serve as a good appli- 
cation of the principles enunciated in this article. 

There are two engines, which we will designate 
as Xp. 1 and No. 2. Xo. 1 is a high-pressure engine, 
uses steam of 105 pounds pressure for gauge, and 
cuts off at quarter stroke. No. 2 is a condensing 
engine, uses steam of 20 pounds pressure, and cuts 
off at half stroke. The feed water is 100° in both 
cases. The back pressure in the condensing engine 
is 2 pounds per square inch, and the friction of the 
unloaded engine is 2.5 pounds per square inch in 
each engine. 

Which will develop the greatest mechanical effect 
from one cubic foot of water evaporated, and how 
much coal will be required for No. 1 engine to evapo- 
rate the water, if 10 pounds are required for No. 2 ? 

For No. 1 : 

1.38 = mechanical effect during expansion. 

(1 + 1.38) X l-<^ -^ 4 = 71.4 = mean pressure. 

But as the steam exhausts into the atmosphere, 
and 2.5 pounds per square inch are required to over- 
come friction, 

71.4 — 15 — 2.5 = 53.9 = mean effective pressure! 

For No. 2 : 

.69 = mechanical effect during expansion. 



EXPANSION OF STEAM. 87 

(1 + .69) X 35 -7- 2 =z 29.575 = mean pressure. 

Deducting the back pressure and friction, 

29.575 — 2 — 2.5 = 25.075 zz mean effective pres- 
sure. 

Now let us suppose that the steam acts in both 
cases in a cylinder of one square inch cross section, 
and a stroke of one foot. As the volume of steam 
of 105 pounds pressure is 251 times as great as that 
of the water from which it is generated, one cubic 
foot, or 1728 cubic inches of water, will generate 
1728 X 251 =z 433728 cubic inches of steam. 

The steam being cut off at quarter stroke, three 
cubic inches of steam are used at each stroke, and 
the number of strokes made by No. 1 engine will be 
433728 -r- 3 = 144576. 

The distance in feet travelled by the piston, mul- 
tiplied by the mean pressure, gives the mechanical 
effect. 

The distance in feet is 

144576 X 1 = 144576. 
Hence the mechanical effect is 

144576 X 53.9 = 7792646.4 
For No. 2 the relative volume of the steam and 
water is 767, and one cubic foot of water generates 
1728 X 767 = 1325376 cubic inches of steam. 
As 6 inches of steam are used at each stroke, 
1325376 -^ 6 z= 220896 zz number of strokes. 
Hence the mechanical effect is 

220896 X 25.075 zz 5538967.2. 



88 THE CADET ENGINEER 

Calling the mechanical effect of No. 2 unity, that 
of No. 1 is 

7792646.4 ^ 5538967.2 = 1.406. 
So that the per cent, of gain by No. 1 is 

.406 X 100 = 40.6. 
Now let us find the coal required for No. 1. The 
total heat in the steam of No. 2 engine is 1193^.45, 
and since the temperature of the feed water is 100°, 

11930.45 _ 100° zz: 1093^.45 zz heat imparted to 
a cubic foot of water by the consumption of 10 pounds 
of coal. 

The total heat in the steam of No. 2 engine is 
1219°.36, and 

1219°.36 — 100° = 1119°.36 = heat required to 
be imparted to a cubic foot of water. 

If 10 pounds of coal are needed in the first case, 
we shall now require 

(1119°.36 X 10) ^ 1093°.45 zz 10.237 pounds. 

§ 10. Cut-Offs. 

As a necessary sequence to the .subject of expan- 
sion, we have cut-offs, or arrangements by which 
the steam is shut off from the cylinder before the 
piston has completed its stroke. We will briefly 
notice a few of these. 

The cut-off first in use on beam engines, when 
single puppet valves and one eccentric were employed, 
is represented in Fig. 27. There are two cams, D D, 



CUT-OFFS. 



89 



on opposite sides of the main shaft C. As the shaft 
revolves, these cams strike the adjustable piece H, 



;.,.-... ,,,.... ..,,,,.,,..,,.,,,.. ,,„.,,,,,,.,„,,..^..-,...^^^._- ..,,..-..^...^,. ,-- - ......... 


n 


jrig.27. ^^ 

/ A 


B 


\ /^ 






E 

r~^ i 




L 




Vl- . 


' 





and raise the cam board E, thereby opening the 
throttle valve B. When contact ceases between the 
cam and the piece H, the throttle valve closes and 
the steam is cut off. By moving the piece H to the 
ri2:ht or left, we can make the time of contact, more 



90 THE CADET ENGINEER. 

or less, at pleasure. The cam board must be raised 
and secured to the support L, to insure a supply of 
steam, when working the engine by hand. 

The great objection to" this cut-off, is the amount 
of clearance incident on its use ; a large proportion 
of the steam in the side pipe, and in the steam pipe, 
in advance of the valve B, being expended at each 
stroke for which we get no return except from its 
expansion. 

In 1846, Sickels's cut-off was introduced. In this 
arrangement the valve is detached from the lifting 
rod, at any desired point of the stroke, and falls to 
its seat. A dash pot is used to keep the valve from 
seating too hard. In the earlier forms of Sickels's 
cut-off, the valve had to be tripped by the time the 
piston arrived at the middle of its stroke, or not at 
all. As constructed at present, however, the valve 
may be closed at any desired portion of the stroke. 

Stevens's cut-off next made its appearance. Though 
not readily adjustable, it has been very successful, 
and continues to give satisfaction. In this cut-off 
there are two eccentrics ; one for the steam valves, 
and the other for the exhaust. The steam eccentric 
has great throw, and opens the valve by means of a 
toe and lifter. While there is contact between the 
toe and lifter, the valve is open, so that the point of 
cutting off is varied by making this contact of any 
required duration. 

Cut-offs are so numerous, that it is impossible to 
notice all the varieties. Allen and Wells's arrange- 



CUT-OFFS. 



91 



ment, and Winter's, complete the list of cut-ofFs that 
have been applied to any great extent to steamers 
fitted with puppet valves. 

In Allen and Wells' cut-ofF, the lifting toe is raised 
by a cross arm on the rock shaft arm, but can be 
shifted from this at any point of the stroke and 
made to descend on an arm having motion coincident 
with the piston. This cut-off is readily adjustable. 




92 THE CADET ENGINEER. 

A sketch of Winter's cut-ofF is given in Fig. 28. 
A, the rock shaft, is made to revolve by the eccen- 
tric. B is a cam on the rock shaft which revolves 
with the shaft and raises the adjustable toe C, which 
in turn raises the lifter D, and thereby opens the 
valve. When contact between B and C ceases, the 
valve is closed. So, by moving the adjustable toe C, 
to the right or left, we can cut off the steam at a 
given point of the stroke. 

Let us now look at some of the means employed 
to cut off the steam when a slide valve is used. The 
first plan was to put on lap, or elongate the valve 
face on the steam side. But such a cut-off was not 
adjustable, and, moreover, had very restricted limits. 
A second valve chest was then put on above the 
chest in which the main valve worked, and a valve 
was introduced to regulate the admission of steam to 
the main steam chest. By this means, although the 
main steam valve might be open, if the supply of 
steam to the main steam chest was shut off, it would 
also be shut off from the cylinder. 

This secondary valve, from the number of its ports, 
is called a gridiron valve. But this arrangement is 
not readily adjustable. 

An English cut-off for slide valves, introduced into 
this country by Messrs. Merrick & Son, may be de- 
scribed as follows : There are two cut-off valves on 
the back of the main valve, which, covering the 
openings in the main valve at any desired point of 
the stroke, cut off the steam. These cut-off valves 



CUT-OFFS. 



93 



are easily adjustable by means of a wheel, and right 
and left-handed screws on the stem. 

In Green's cut-off, represented in Fig. 29, there 
are toes and lifters, acting directly on the steam 
valves, ah c d is a section of the steam chest, e 
and / are the steam ports, g and Ti the steam valves. 
The steam ports are made long and narrow, so as to 




give a large opening for a small throw. A, corres- 
ponding to the rock shaft, is a flat piece of metal 
receiving a rectilinear motion to and fro, from the 
eccentric. It has four guides, m m m m, to keep it 



94 THE CADET ENGINEER. 

in position. B B are the lifting toes fitting into 
slots cut into the piece A. There are flat springs m 
m under them, so that if forced down by pressure, 
they will return to their original positions when the 
pressure is removed. There are also lugs on the 
back of these toes which strike against an adjustable 
guard, whereby the height to which the toes rise, 
can be varied. The action of the cut-off is as follows : 
If A is moving in the direction indicated by the 
arrow, the toe B will strike against the lifter C, and 
open the valve A. When contact between B and C 
ceases, the weight E will close the valve. Mean- 
while, the top of the other toe striking against the 
rounded side of the lifter, is pressed down without 
moving the valve until contact ceases, when the 
spring m forces it up to its former position. It will 
thus be seen, that to alter the point of cutting off, 
w^e have only to move the adjustable guard, thereby 
raising or lowering the toes and making contact 
between them and the lifters of more or less duration. 
The link motion is sometimes represented as a 
cut-off; but to use a homely expression, it is not a 
pure cut-off, but a mixture of a cutK)ff and a squeeze- 
off. As the link is moved towards the centre, not 
only is the point at which the valve closes changed, 
so that the steam is cut off sooner, but the travel 
of the valve is also reduced, so that the steam is 
throttled. 



I 



THE INDICATOR. 95 



§ 11. The Indicator. 

The steam-engine indicator consists essentially of 
a small steam cylinder, connected with the main 
cylinder by a pipe and stop-cock. There is a close 
fitting piston in this small cylinder, and above the 
piston is a spiral spring, which indicates by its scale 
the number of pounds pressure per square inch on 
the piston. There is also a parallel cylinder, covered 
with paper, which is made to revolve back and forth 
about I of a revolution. A pencil attached to the 
piston of the steam cylinder traces a figure on this 
paper when the engine is in motion, showing the 
pressure on the piston at any point of the stroke. 
The cylinder on which the paper is placed must have 
motion coincident with that of the piston in the 
cylinder to which the indicator is attached. The 
figure made by the pencil is called an indicator, 
diagram or card. By an inspection of the diagrams 
from an engine, we can readily determine the mean 
pressure on the piston, the horse-power, the state of 
the vacuum, where the valves open and shut, etc., etc. 

In the use of the indicator, as generally constructed 
in this country, much trouble is experienced in fast 
working engines by the piston jumping when steam 
is admitted to the cylinder, and making a waving 
line at the top of the diagram. Porter's indicator, 
represented in Fig. 30, obviates this in a great mear 
sure. A is the steam cylinder, and C the piston rod. 



96 THE CADET ENGINEER. 

The arm B on the cylinder carries the bars and rod 
of a parallel motion. The pencil is inserted in the 
hole D, so that it has a motion coincident with and 







T^i'ri ^ft 


^1 


E 

■ ' - 









> \v- ■ ■ h^ 1 


"^^^d^ 


p ^ 






'■■'-■" - -:■-•' ^Ji_ : J 



in the same direction as that of the piston. The 
pencil is put on to the paper stretched on the cylinder 
E by turning the arm B on the steam cylinder. P 
is a clamp and bracket, connecting the two cylinders. 

is the spring for keeping the paper stretched tightly. 

1 and H are pulleys, around which a cord is passed. 



THE INDICATOK. . 97 

and attached to the proper part of the engine, whereby 
the cylinder E receives the required motion. 

It will be observed that on account of the manner 
in which the pencil is attached, it will receive a con- 
siderable motion up or down for a very small motion 
of the indicator piston. This shows the reason of 
its smooth working, when applied to engines making 
a considerable number of revolutions per minute. 
As the indicator piston has only to rise and fall a 
very short distance, the spiral spring connected with 
it is stronger than those made for indicators of the 
usual construction. Now let us suppose the indicator 
to be attached to the engine from which we wish to 
take a diagram, the string which causes the motion 
of the paper cylinder being connected with a part 
of the engine having motion coincident with that of 
the piston. Some indicators are fitted with a small 
plug-cock in the steam cylinder, whereby all the 
water may be blown out of the pipe. But if this is 
not the case, the water must be blown out of the 
pipe by opening the stop-cock before the indicator is 
attached. When this is done, open the stop-cock 
and warm the steam cylinder of the indicator. Then 
close the stop-cock, and the piston will stand at the 
point marked on the scale. K the pencil be put 
on the paper, the cylinder revolving, a horizontal 
line will be traced, and this we call the atmospheric 
line. The piston should then be forced down, until it 
stands at 15 pounds, and in that position, if the pencil 
be put on the paper, the perfect vacuum line will be 



98 



THE CADET ENGINEER. 



traced. Everything is then ready to take the dia- 
gram ; to do which we have only to open the stop- 
cock, and put the pencil on the paper. If we suppose 
the valve to have neither lap nor lead, and the 
engine to be perfect in its action (which is, of course, 
only a theoretical case), the diagram will be the 
rectangle A B C D, Fig. 31. E F is the atmospheric 
line, traced by the pencil, when the stop-cock is 




closed, and D C is the perfect vacuum line. Now, 
when the crank is on the centre steam is admitted, 
the piston rises a distance proportionate to the amount 
of pressure, and the pencil traces the line D A, called 
the receiving line. As the main piston makes a 
stroK:e, the paper cylinder revolves, and the pencil 
traces the horizontal line A B, the steam line, the 
indicator piston being kept up on a level with the 
point A by the pressure in the main cylinder. When 
the main piston arrives at the other end of the 



THE INDICATOR. 99 

stroke, the exhaust valve is opened, and the pressure 
falls to the perfect vacuum line, causing the pencil 
to describe the line B C, the exhaust line. On the 
return stroke of the main piston, there will be a 
perfect vacuum in the cyhnder, and the pencil will 
trace the line C D, the vacuum line. If the steam 
valve was set wdth lead, or so as to open before the 
end of the stroke, the steam line w^ould have the 
direction a A. If the exhaust valve had lead, g C 
would represent the exhaust line, instead of B C. 
The exhaust valve is often made to close before the 
end of the stroke, so as to produce cushioning, and 
this would appear in our theoretical card as the 
hyperbola h c. If the steam valve opened too late, 
the receiving Ime would take the position D e. 

(It will be understood that these are extreme cases, 
as represented in the diagram, and made so to aid in 
showing the principle clearly.) If the exhaust vah e 
opened too late, the exhaust line would appear as 
B ^. By accustoming himself to the meaning of the 
various directions taken by these several lines, an 
engineer can tell at once, on seeing a diagram, 
whether the engine from which it was taken is in 
good running order. 

In the practical case of a diagram from an engine, 
the vacuum line would appear above the perfect 
vacuum line, as at o s, and the perpendicular distance 
between this line and the perfect vacuum line is the 
hack jpressiire. The corner at A will be square if the 
valve is set rightly, and the ports are of sufficient 



100 



THE CADET ENGINEEE. 



size. The corner at B has a slight rounding from 
where the exhaust valve opens at g. The corner a 
should be square, or nearly so. A g r s o q will then 
represent what is called a good diagram from a non- 
expansive engine. 

In the case of an expansive engine, the theoretical 
curve of expansion will be an hyperbola. We have 
already shown one method of laying out the curve 
in the article on expansion, but we will indicate 
another, that will be found useful in connection witji 
diagrams. In Fig. 32 A B is the atmospheric line, 
and C D is the perfect vacuum Hue ; C E is the 




receiving line, E F the steam line, and at F the 
steam is cut off, and the pencil describes the hyper- 
bola ¥ a h c d, called the expansion line. We can 
lay this out merely by applying Mariotte's law. 



THE INDICATOR. 101 

Divide the ^Yhole length of stroke C D into any 
number of equal parts, and observe how many of 
those parts the steam follows. In the case under 
consideration, the initial pressure of the steam is 22 
pounds, and the steam follows two of the spaces into 
which we have di^dded the stroke. Then when the 
steam reaches the third space, its volume will be 1^ 
times what it was originally, and its pressure will 
therefore be | of 22, or 14| pounds. Similarly, as 
at the fourth division the volume is doubled, the 
pressure will be ^ of 22, or 11 pounds. At the fifth 
division the volume is 2^ times its original bulk, and 
the pressure is | of 22, or 8| pounds, and so on. 
When all the points are found, describe the curve 
¥ ah c d. E¥ ah c d D C is then the theoretical 
diagram, taken from an engine carrj-ing 7 pounds of 
steam per gauge, and following i of the stroke. 

In the practical case the curve will usually fall a 
little below the theoretical curve. If it is very much 
below, it is caused by a leak, either in the exhaust 
valve or around the piston. If the actual curve is 
above the theoretical, it will be on account of a leak 
in the steam valve, whereby steam is admitted to 
the cyHnder after the valve is closed. Our practical 
diagram is ¥ F g h k I m ef. In drawing the theo- 
retical curve on a diagram taken from an expansive 
engine, it must be remembered that all the steam in 
the clearance also expands. This clearance then 
must be reduced to an equivalent length of cyHnder, 
and added to the end of the stroke. 



102 THE CADET ENGINEER. 

In the ease of a diagram taken from a high pres- 
sure engine, the whole card would appear above the 
atmospheric line, as the steam exhausts into the 
open air. The perpendicular distance between the 
lower line of the diagram and the atmospheric line 
would indicate the resistance to the motion of the 
piston, caused by vapor in the cylinder, obstacles to 
a free exhaust, and the like. The back pressure 
would be this pressure, plus the pressure of the atmos- 
phere into which the steam exhausts. 

The common way of finding the actual horse-power 
of an engine is by means of a diagram. That is, we 
get the most important thing, the mean pressure of 
the steam from the diagram. A horse-power, as 
agreed upon by all engineers, is the power required 
to raise 33,000 pounds one foot high in a minute. 
Hence, when we know the mean pressure per square 
inch on the piston, we can readily find the total 
pressure acting on its whole area. This being mul- 
tiplied by the distance in feet that the piston travels 
per minute, will give the number of pounds raised 
one foot high in a minute by the piston. But as 
every 33,000 of these pounds represents one horse- 
power, we have only to divide by 33,000, and the 
operation is complete. 

Example. — Let ABODE, Fig. 33, represent the 
diagram from which we propose to ascertain the 
mean pressure. Divide the atmospheric line, or the 
perfect vacuum line, into any number of equal parts, 
and erect perpendiculars at every point of division. 



THE IXDICATOR. 



103 



measure the effective pressure 




Then with a scale 
between each of 
these perpendicu- 
lars. (A scale 
can readily be 
constructed by 
observing that 
the perpendicu- 
lar distance be- 
tween the atmos- 
pheric and per- 
fect vacuum lines 
is 15 pounds on 
the scale.) Thus, 
between the first and second perpendiculars, the total 
pressure is 32 pounds, and the back pressure is 3 
pounds, so that the effective pressure is 29 pounds. 
Measuring the pressure between all the perpendicu- 
lars, we have 

(29 + 29 -h 29 + 29 + 24.5 -f 20.7 + 17.8 + 13) -f- 
8 1= 24, as the mean effective pressure per square 
inch on the piston. (The mean effective pressure 
on the diagram taken from the other end of the 
cylinder, at a short interval from the time the dia- 
gram under consideration was made, should then be 
calculated. If the two results differ, take their mean 
as the pressure per square inch to be used in the 
calculation.) Now we will suppose the cylinder, 
from which this diagram was taken, to have a 
diameter of 60 inches and a stroke of 10 feet. We 



104 THE CADET EKGINEER. 

will also suppose that the engine was making 20 
revolutions per minute when the card was taken. 
(The speed of the engine, when a card is taken, 
should always be carefully noted for future reference.) 
Then the mean pressure acting on the piston is 
2827.4X24=1:67857.6 pounds. As the engine is 
making 20 revolutions per minute, the distance passed 
over by the piston in that time islOX2X20=z:400 
feet. Hence, the power exerted by the engine is 
equivalent to 67857.6 X 400 =z 27143040 pounds 
raised one foot high in one minute, and the horse- 
power is 

27143040 -f- 33000 = 822.5. 

To find the useful horse-power of the engine, we 
must remove the load and take a diagram, for the 
purpose of finding the mean pressure per square 
inch exerted in overcoming friction. We can then 
subtract this from the mean pressure acting on the 
piston when the load is on the engine, and that will 
give the mean pressure per square inch producing 
useful effect, or we can find the horse-power required 
to overcome friction, and subtract it from the total 
horse-power developed by the engine. 

Example. — Suppose that the diagram we have 
been considering in the previous example, was taken 
from a stationary engine when performing its average 
work. Then let us suppose the load to be taken off*, 
so that the engine has only the friction of its parts 
to overcome. When it is making 20 revolutions per 



THE INDICATOR. 105 

minute, under these conditions, if we apply the in- 
dicator, we shall take a friction diagram. The mean 
pressure per square inch acting on the piston can 
then be calculated from this diagram, precisely as in 
the previous case. Let us suppose this pressure to 
be 2.5 pounds per square inch, it is then required to 
find the horse-power, producing useful effect, de- 
veloped by the engine. 

1st Solution. The mean pressure per square inch 
producing useful effect is 24 — 2.5 = 21.5 pounds. 
Hence the useful horse power is 

(2827.4 X 21.5 X 400) ^ 33000 = 736.8. 

2d Solution. As the mean pressure per square 
inch required to overcome friction is 2.5 pounds, the 
horse-power absorbed by friction is 

(2827.4 X 2.5 X 400) -r- 33000 zz 85.7. 

Hence the horse-power producing useful effect is 
-^22.5 — 85.7 zz 736.8. 

The horse-power of a boiler can also be calculated 
by the aid of an indicator diagram. In the case of 
a boiler, every cubic foot of water evaporated per 
hour is considered equivalent to a horse-power. 
From a diagram we can ascertain how many cubic 
feet of steam are used in an hour, and, consequently, 
how much water has been evaporated. But the 
more usual calculation in regard to the efficiency of 
a boiler, is the number of pounds of water evaporated 
per pound of coal. Let us take an example. 

A B C D, Fig. 34, represents a card taken from a 



106 



THE CADET ENGINEER. 




direct-acting propeller engine. We have given the 
following data : diameter of cylinder, 63 inches ; 
length of stroke, 3 feet; revolutions per minute, 60; 

clearance at 
each end of 
cylinder, re- 
d u c e d to 
equivalent 
length of cyl- 
inder, 1 inch ; 
pounds of coal 
consumed per 
hour, 1500; 
loss by blowing off, 15 per cent. It is required to 
find the number of pounds of water evaporated by 
the consumption of one pound of coal. At B, as 
indicated by the card, the steam is cut off, and 
expands through the remainder of the stroke. B is 
at one-quarter of the stroke, so we see that we use 
one-quarter of a cylinder full of steam of 23 pounds 
pressure, plus the clearance, at each stroke. Or, we 
can find the terminal pressure, as indicated by the 
diagram, by continuing the expansion line, as its 
path evidently would be but for the exhaust lead, to 
where it cuts the perpendicular c c?, drawn one inch 
from the end of the stroke to include the clearance. 
This terminal pressure C I being 5 pounds above a 
perfect vacuum, shows that there is a cyhnder full 
of steam, plus the clearance, of 5 pounds pressure, 
used at each stroke. 



THE I^'DICATOR. 107 

By taking the fraction of the cylinder filled with 
steam, as in the first case, we lose all the steam that 
leaks into the cylinder, if the valves are not tight. 
In the second case we lose all the steam that con- 
denses in the cylinder, and leaks past the piston or 
through the stuffing-box. Still the last method is 
the most correct, and is generally employed. It is 
evident that in neither case can we obtain all the 
steam that is generated, since that lost by leakage 
cannot be calculated. 

We will use the terminal pressure in solving this 
example. The method, however, is the same' in 
either case. 

The quantity of steam used at each stroke will be 
the capacity of the cylinder plus the clearance, or, 
21.647 X 4.0833 = 87.39 cubic feet. 

In an hour the engine makes : 

60 X 2 X 60 = 7200 strokes. 

Therefore, 87.39 X 7200 =z 629208 cubic feet of 
steam used in an hour. But the relative volume of 
steam at 5 pounds pressure, and water, is 4769. So 
that 

629208-4769 = 131.93 cubic feet of water eva- 
porated per hour. As a cubic foot of sea water 
weighs 64.3 pounds, 

131.93 X 64.3 zz 8483.1 pounds of water evapor- 
ated per hour. Now, the 1500 pounds of coal con- 
sumed in an hour, both evaporates this water and 
heats the water blown off. And since 15 per cent. 



108 THE CADET ENGINEER. 

of heat is lost by blowing off, 1500— (1500 X -15) 
1=1275 pounds of coal, evaporate 8483.1 pounds of 
water. Therefore, 

8483.1 ~ 1275 = 6.66 pounds of water, evaporated 
by one pound of coal. 

Another way of introducing the loss by blowing 
off, is as follows : Since 1500 pounds of coal evapor- 
ates 8483.1 pounds of water, 1 pound of coal will 
evaporate 

8483.1 ^ 1500 = 5.66 pounds of water. 

But, as 15 per cent, of heat is lost, the 5.66 pounds 
of water only represents 85 per cent, of the real 
efficacy of the coal, and the water evaporated by one 
pound of coal will be 

5.66 X 100 — 85 =: 6.66 pounds. 

§ 12. The Slide Valve. 

A three-ported slide valve in its simplest form is 
represented in Fig. 35. The valve has the position 
shown in the sketch, when the piston is at one end 
of the stroke. When the piston commences to move, 
the valve also receives motion from the eccentric. 
If it moves to the right, the port A will be uncovered 
and steam will be admitted into one end of the 
cylinder, while the port B will be open to the exhaust 
port C, and the steam in the other end of the cylinder 
will be exhausting. When the valve has moved far 
enough to uncover the port A, (at which time the 



THE SLIDE VALVE. 



109 




piston will have made half a stroke), it commences 
to move to the left, and at the termination of the 
stroke, the 
port A will 
again be 
closed. n 
the return 
stroke of the 
piston, the 
valve will continue to move to the left until the port 
B is fully open, when it will again move to the right, 
closing the port B at the termination of the stroke. 
It is evident that the motions of the valve and piston 
are at right angles ; for the valve is at half stroke 
when the piston has completed its stroke, and vice 
versa. So to set the eccentric of this valve, we have 
only to make the line joining the centre of the 
eccentric and the centre of the shaft, perpendicular 
to the line joining the centre of the crank-pin and 
the centre of the shaft. The throw of the eccentric, 
or the travel of the valve, (supposing the eccentric 
rod to be directly connected to the valve stem), is 
evidently equal to twice the breadth of the steam 
port, and the face of the valve is just as wide as the 
steam port. 

With the valve set in this manner, the steam is 
not admitted to the cylinder until the crank is on 
the centre. But it is found desirable to admit steam 
a little before the end of the stroke ; and this can 
readily be accomplished by turning the eccentric on 



110 THE CADET ENGINEER. 

the shaft. This we call giving the valve lead. 
Thus, if the steam port is open a sixteenth of an 
inchj when the crank is on the centre, we say that 
the valve has a sixteenth of an inch lead. But if 
we open the steam port A before the end of the 
stroke, we also open the port B to the exhaust, and 
the amount of this opening at the termination of the 
stroke, we term the exhaust lead. 

Now, if we wish the port to be closed before the 
termination of the stroke, we make the face of the 
valve longer, or put on lap. In this case the throw 
of the valve must be increased by an amount equal 
to twice the lap. But if excessive lap be put on, it 
is evident that the travel will be so much increased 
as to permit the steam to exhaust at an early part 
of the stroke. To obviate this, we must put lap on 
the exhaust side of the valve. This has a bad effect 
in causing the exhaust valve to close too soon. This 
will be seen clearly in the illustration of the geomet- 
rical action of the slide valve, Fig. 36. Let AB 
equal the length of stroke of our engine drawn to 
any scale. We will give the valve an amount of lap 
on the steam side equal to half the breadth of the 
steam port. The travel of the valve will then be 
equal to three times the breadth of the steam port. 
On A B, as a diameter, describe a circle which will 
represent the path described by the centre of the 
crank-pin, while the piston is travelling twice the 
distance A B. Divide this circle into any number 
of equal parts, and draw perpendiculars to A B from 



THE SLIDE VALVE. 



ill 



every point of division. We shall thus determine 
the position of the piston corresponding to that of 



Mg.3ff. 



- ' ' ' \ A 



,i./..-_L/- 



cA-^-^'^a 



y ■'^,A -^B 



:;h^ 



-f^ *7,^y, 



the crank at various points. With the same centre 



112 THE CADET ENGINEEK. 

t, as that of the circle A r B «, describe a circle C o 
D ^, having the travel of the valve for its diameter. 
This will represent the path of the centre of the 
eccentric, during a revolution of the crank. When 
the crank is on the centre, the line connecting the 
centre of the crank-pin and the centre of the shaft 
will be A ^ ; so that if the valve had neither lap nor 
lead, the line connecting the centre of the eccentric 
and the centre of the shaft should take the direction 
t r, perpendicular to A t. But in the present case, 
when we have both lap and lead, we make t u equal 
to the sum of the lap and lead, and through u, draw 
a line parallel to t r. Connect the point o where 
this line cuts the circle with the centre, and o t will 
be the proper position for the line connecting the 
centre of the eccentric and the centre of the shaft, 
when the crank is on one centre. When the crank 
is on the other centre, this line will appear at t F. 
Divide the circle C o D ^ into the same number of 
equal parts as we divided the circle A r B 5, and 
draw perpendiculars to o^ from every point of divi- 
sion. The lengths of these perpendiculars show the 
distances travelled by the valve at various points. 
Now, let A B represent the centre of the exhaust 
port. Then draw a h and c d to represent the width 
of one steam port, and ef and g li for the other. 
Make a i equal to I w, the steam lead, and draw a 
line i h parallel to a h. This is the line to which all 
our measurements must be referred since the valve 
commences to move from this position. Thus, when 



THE SLIDE VALVE. 113 

the crank has moved the distance A 1, the centre of 
the eccentric has moved the distance o 1, and the 
perpendicular distance of this point 1 from o p will 
be the distance the valve has travelled. Lay off this 
distance below the line i h on the first perpendicular, 
and the point so determined will represent one 
position of the valve. Similarly, when the crank 
has travelled the distance A 2, the centre of the 
eccentric has passed over o 2, and the valve has 
travelled the perpendicular distance between 2 and 
op. Lay off this distance on the second perpen- 
dicular below i k, and we determine the position of 
the valve at another point of the stroke. Find the 
position of the valve in this manner at every point 
of division, and through the points so found draw a 
curve which will represent all the positions of the 
valve during one revolution of the crank. It must 
be observed, in laying off perpendicular distances 
from o p, that all points to the right of o ^ are posi- 
tive, and are laid off below i 7c, while all points to 
the left of o ^ are negative, and must be laid off above 
i 7c. We have not yet determined the amount of 
exhaust lap, but this can readily be fixed, now that 
the motion of the valve is represented. When the 
piston has made one stroke, the crank is at B and 
the valve is at P. Now, if the face of the valve was 
only 1^ times the width of the port, the whole port 
would be open for the steam to exhaust. So we 
must put lap on the exhaust side of the valve, and 

we put on enough to have the exhaust lead equal to 
8 



114 THE CADET ENGINEER. 

H I. This gives us the width, w E, of the valve 
face. 

From the curve A i P, we can readily find the 
position of the valve, corresponding to any position 
of the piston. Thus, when the piston has travelled 
the distance A q, the valve is at v, and the distance 
the port is open is equal to the perpendicular dis- 
tance between v and the top of the port a h. At x, 
where the curve cuts a h, the port is closed, and the 
steam expands during the remainder of the stroke 
from y to B. 

We can readily lay down the curve described by 
the lower extremity of the valve. The distance e m 
between ef, the top of the port, and m n, is the 
exhaust lead, and we have only to transfer the dis- 
tances of the various points in the first curve from 
i k to their respective distances from m n, on the 
same perpendicular on which they were first laid 
down. By this curve we see that the exhaust open- 
ing is closed at/, when the piston has travelled the 
distance A z. The steam being pent up in the 
cylinder, from z to B, occasions excessive cushioning, 
and that is the reason why expansion by means of 
lap on a slide valve cannot be carried to any great 
extent. About two-thirds of the stroke is the earliest 
point at which a slide valve should close the steam 
port. 

In setting slide valves, it is a common practice 
with engineers to set the eccentric so that the valve 
shall have from 3^ to |^ of an inch steam lead, accord- 



THE SLIDE VALVE. 115 

ing to the size of the engine and number of revolu- 
tions. This is generally considered a great abun- 
dance, to make the engine work smoothly and effi- 
ciently. Therefore, when the engine is in motion, 
if there should be any thumping, the first thought 
of the engineer is, that the connecting rod or pillow 
block brasses are slack, and require setting up. As 
he set the valve himself, saw that it had | or ;| inch 
steam lead, as the case may be, he is sure that there 
is no trouble in that quarter. So the brasses are 
keyed up, and as a natural consequence get hot, and 
the engineer will ruin the journals by continually 
running cold water on them. 

If the engine has the link motion, as soon as a 
thump is heard the engineer usually runs up the 
link until the engine works smoothly. By this action 
the travel of the valve is diminished, so that the 
steam is throttled or wire drawn, and there is an 
excessive cushioning of the exhaust steam, so that 
the engine is not developing all the power that it 
should. 

An indicator diagram is frequently taken when an 
engine thumps, and in nine cases out of ten it shows 
a want of steam lead. But as the engineer saw the 
lead when the valve was set, of course the indicator 
is wrong, and he goes on in his vain endeavors to 
stop by keying up a thump caused by want of steam 
lead. The authors of this work, while on duty at 
the Norfolk Navy Yard, have set more than a 
hundred slide valves (at the suggestion of Fleet 



116 THE CADET ENGINEEE. 

Engineer Theodore Zeller, U. S. N.) on the following 
plan : One-eighth of an inch is allowed for the lost 
motion of the shaft, and ^ of an inch for every con- 
nection between the eccentric and the valve. Thus, 
if there were six connections, we allow -^ for each, 
making | and | for the shaft, making i inch, to which 
w^e add Jg for actual lead. So in setting the valve 
we give it -f^ of an inch apparent lead, but when the 
engine is in motion, i inch of this lead is annihilated 
by lost motion, and the valve will only have -^ of 
an inch lead, as contemplated. 

When the slide valve of an engine is set in this 
manner, the engine will work smoothly, and will 
show no hesitation in passing the centres ; there will 
be no thumping or jarring, and the plague of hot 
journals will be unknown, as a general thing. Ex- 
perience confirms the truth of this statement, and 
the indicator shows that the theory is a correct one. 
Engineers are too apt to consider that the indicator 
is out of order when a diagram does not suit them, 
but they should recollect that an indicator must be 
very much deranged when it will not show the lead 
of a valve correctly. 

The foregoing method of setting slide valves is ear- 
nestly recommended to the attention of all engineers. 
Even if they do not believe in it, let them test it. 
Anything promising such important results is cer- 
tainly worth a trial, and we are sure that they will 
not regret having made the experiment. 



BALANCED VALVES. 117 



§ 13. Balanced Valves. 

In the use of single puppet valves much difficulty 
was experienced in working an engine by hand, 
unless a very long starting bar, or an arrangement 
of levers, was employed. But the great objection is 
the power required to work these valves while the 
engine is in motion. This led to the adoption of the 
double puppet valve, consisting of two single valves 
connected to one stem. Theoretically the upper and 
lower parts of this valve should be of the same 
diameter. But the upper half of the steam valve is 
made a little larger, since if we neglect the weight 
of the valve, lifting rod, etc., and suppose both halves 
of the valve to be equal, then there will be an equi- 
librium, and the valve will remain in any position 
in which it may be placed. But in the case of the 
exhaust valve, the lower half is made the largest, so 
as to give security against the valve being forced 
from its seat by the pressure of steam. 

The Cornish valve is balanced, and partakes of 
the nature of a double puppet valve. The seat of 
the valve is similar to a double puppet valve turned 
upside down, and the valve answers to the reversed 
seat of the double puppet valve. 

The arrangements for relieving the pressure on 
the back of slide valves are numerous and varied. 
Prominent among these is the ring on the back of 
the valve. This is illustrated in the sketch of the 



118 



THE CADET ENGINEER. 



double ported valve, Fig. 37. On the back of the 
valve is a ring C C secured to the steam chest, 
against which the valve works steam tight. D is a 




pipe connecting the interior of the ring with the con- 
denser. By this means, as there is a vacuum within 
the ring, the pressure is taken off so much of the 
back of the valve as the ring encloses. The ring is 
sometimes secured to the back of the valve, instead 
of to the steam chest. But the arrangement indicated 
in the figure is the best, since the ring can readily 
be adjusted at any time by the set screws, whereas, 
when the ring is secured to the valve, the bonnet of 
the steam chest must be removed to set up the pack- 
ing. Instead of the pipe D, a hole might be cut 
through the back of the valve, opening communi- 
cation with the exhaust port, and so taking the 
pressure off the back. But by this arrangement we 



BALANCED VALVES. 



119 



could not tell whether the ring leaked or not. In 
the present case, however, by removing the pipe or 
breaking a joint, we can see at once whether any 
steam escapes past the ring. 

Bristol's roller valve has been applied to govern- 
ment vessels to a great extent. It is a common three- 
ported valve, and is not balanced, but the pressure 
on the back is taken on steel rollers working on steel 
seats on the face. This valve seems to give satis- 
factory results. 

The box valve is like a box with or without a top, 
having an opening in it equal to a large proportion 




120 



THE CADET ENGINEER. 



of the area of the valve. A valve of a similar char- 
acter, but possessing several novel features, is repre- 
sented in Fig. 38. A and B are the ports, commu- 
nicating with the two ends of the cylinder. The 
valve C is open on the inside, and works steam-tight 
against a ba*ck, D. The opening in the centre of the 
valve is the exhaust port, and communicates directly 
with the condenser E. The backing D is connected 
with the exhaust pipe, and can be kept up against 
the valve by means of the screw and spiral spring. 
F is the steam pipe passing through the condenser. 
The action of this valve will be apparent. 

The piston valve consists of a pipe having a piston 

at each end, work- 
ing in a cylindri- 
cal valve chest. 
The opening in 
the pipe forms the 
exhaust port. 
This is also an 
equilibrium 
valve. 

Fig. 39 shows a 
cross section of a 
balanced valve, 
partaking of the 
nature of a plug 
cock. A and B 
are the steam 
ports, and C is the exhaust. The steam enters the 




BALANCED VALVES. 



121 



spaces D D of the valve through the openings E E E E, 
and when the valve is made to oscillate, steam is 
admitted at one end, as B from D, and escapes from 
the other end, as A through the exhaust opening H 
into the exhaust port C. It will be seen that the 
upward and downward pressures of the steam in the 
spaces D D are the same ; also that, as there is an 
opening, H, on the top of the valve corresponding to 
and connected with the lower opening H, the exhaust 
portion of the valve is in equilibrium. Theoretically 
this is a very good style of valve, but in practice it 
is found impossible to keep it tight. All those who 
remember the great trouble and enormous expense 
caused by rotary valves on the "Adriatic," will concur 
in condemning them. 

Waddell's balanced valve, Fig. 40, has a ring, B, 




under the top of the valve, instead of on the top. 
By this means there is an upward pressure on the 



122 



THE CADET ENGINEER. 



valve, to relieve so much of the downward pressure 
as is not balanced by the steam ports and the channels 
in the valve seat. 

The valve of the U. S. Steamer, " New Ironsides," 
is double-ported, and slides under a saddle-plate, so 
that the pressure is taken off the back. It is repre- 
sented in Fig. 41. The low^er side of the valve work 
on steel rollers, so as to relieve the weight. 




Davie's balanced valve. Fig. 42, presents the novel 
feature of a valve working in the open air without 
any steam chest. B is the steam pipe, and C the 
steam opening in the valve, D D are the exhaust 
openings, and H H the exhaust ports. E E are the 
cylinder ports. The pressure under the valve is 
relieved by steam in the chamber I, acting by means 
of the flexible diaphragm K on levers and rods press- 
ing against the sector L. 



SATUKATION OF WATER IN" MARINE BOILERS. 123 




§ 14. Saturation of water in marine hoilers, scale, and 
the means of preventing its formation. 

The proportion of saline matter held in solution 
in sea water is from 32 to 38 parts in 1000. Deep 
sea water, from whatever locality, holds nearly the 
same constituents in solution 
average, in 1000 parts, according to Dr. lire : 



containing, on an 



25. Chloride of Sodium, 
5.3 Sulphate of Magnesia, 
3.5 Chloride of Magnesium, 



12-1 THE CADET ENGINEER. 

0.2 Carbonates of Lime and Magnesia, 
0.1 Sulphate of Lime. 

Besides a little sulphate and muriate of potash, 
iodide of sodium, and bromide of magnesium. 

The principal ingredient of the substance called 
scale, which is formed in boilers using sea water, is 
sulphate of lime. Where spring water, or what is 
commonly known as hard water, is used, carbonate 
of lime is the principal ingredient of the scale. It 
will be observed, by a reference to the analysis of 
sea water, that it contains but a small proportion of 
sulphate of lime. It is supposed, however, that when 
the water in the boiler assumes a high temperature, 
the sulphate of magnesia is decomposed, and that 
the sulphur, uniting with lime, forms scale. It is 
also a fact, that the power of water to hold salts of 
lime in solution decreases as the temperature in- 
creases, and that is one reason why boilers carrying 
high steam will form so much more scale than those 
where the pressure is less, each boiler evaporating 
the same amount of water in a given time. As to 
the injurious effects of incrustation, it is enough to 
know that the conducting power of iron is about 
thirty times that of scale, to say nothing of the 
liability of burning the iron, w^hen an excessive 
deposit of scale takes place. Should the water 
attain the concentration of -Jf , it will form a satu- 
rated solution, and common salt will be deposited. 

When sea water is used for the purpose of gene- 



SATURATION OF WATER IX MARINE BOILERS. 125 



rating steam, it is very evi- 
dent that if this process were 
continued for any length of 
time, the result would be, that 
the boiler would soon contain 
nothing but one mass of saline 
matter, and the crown sheets, 
£ues, tubes, and connections 
becoming highly heated, would 
be destroyed, and the boiler 
rendered worthless. To pre- 
vent this injurious effect, every 
marine boiler is provided with 
what is termed a blow valve, 
by means of which a portion 
of the w^ater is occasionally 
blown out, or the blow valve 
is kept partially open all the 
time the engine is in motion, 
w^hich is termed a steady blow\ 
To determine the proper 
amount of water that should 
be blown out, to prevent scale 
forming to an injurious extent, 
and also to prevent any need- 
less expenditure of fuel, ma- 
rine boilers are provided with 
an instrument termed a sali- 
nometer. This is represented 
in Fig. 43, as usually con- 



4 


— 1 


-3. 

-/32 


( 


V 




/ 

\ 




\ 


cfe^ 


^ 





126 THE CADET ENGINEEE. 

structed. It is made of glass in the form represented. 
The slender neck of the instrument is graduated, 
and shows the proportion of saline matter contained 
in the water by the depth to which it sinks. Thus, 
if the point marked ^ stands at the surface of the 
water, we know that the saline matter is in the 
proportion of 1 to 32 by weight, and so on. 

Salinometers are also made of brass, and these are 
more delicate than the glass instruments. It is well 
to have one of them on board a steamer to use as a 
test for the glass salinometers, as these are rarely 
graduated with perfect accuracy. 

There is another point that must also be con- 
sidered. Water at different temperatures varies in 
density, becoming lighter as the temperature increases. 
For this reason the salinometer is graduated for a 
fixed temperature, generally 200° Fahrenheit, and a 
thermometer is used in connection with it, so that 
the water tested may be of the proper temperature. 
But if the water varies a few degrees from the 
standard, we can allow for it by making a correction 
of I of 3^ for every 10°, adding the correction if the 
temperature is greater than 200°, and subtracting if 
it is less. 

It will be observed in the figure, that the divisions 
on the graduated scale are constantly decreasing. 
This is so, because, as the saturation increases, there 
is more of the slender neck out of the water requiring 
to be supported, and less of the instrument immersed 
to support it. We will now explain the method of 



SATURATION OF WATER IN MARINE BOILERS. 127 

graduating a salinometer. This will sometimes be 
found useful on board ship as a test. The instru- 
ment is first put into distilled water at the tempera- 
ture of 200°, and the point o, or F W noted. It is 
then put into sea water at the same temperature, and 
the point 3^2 noted. This water is then boiled down 
to half its bulk, and the point ^ noted, and so the 
operation is continued. 

The thermometer and barometer can be employed 
to ascertain the saturation of the water in the boiler. 
The boiling point of water increases with the density, 
and by observing the temperature at which water 
drawn from the boiler boils in the open air, its 
saturation is made known. 

Annexed is a table of the boiling points of water 
at different densities. 

Density. Boiling Point. 

A 213.2° 



35" 



214.4° 

A 215.5° 

A 216.7° 

A 217.9° 

A 219.1° 

A 220.3° 

A 221.5° 

A 222.7° 

li 223.8° 

a 225.0° 

a 226.1° 



128 



THE CADET ENGINEER. 



Fresh water boils in the open air at a temperature 
of 212°. 

To use the salinometer as a test of the saturation 
of the water in a boiler, a pot is usually attached to 
the boiler, so that water can be let into it and a 
salinometer placed therein. As a specimen of a very 
complete and useful pot, Mr. R. H. Long's deserves 
a notice. 

This is represented 
in Fig. 44 . We copy 
from the inventor's 
explanation. " This 
improvement con- 
sists in attaching 
the cylinder A to 
the cylinder B, hav- 
ing a communication 
C, as a means of 
safety to the hy- 
drometer, perfect ac- 
curacy in testing the 
density of water, and 
insuring the engineer 
against danger from 
scalding, etc. 

The cylinder, or 
other shaped vessel 
A, is connected with 
the boiler by the pipe 
and stop-cock G, the 



i 




SATURATION OF WATER IN MARINE BOILERS. 129 

pipe G being closed at the top and having openings 
on the side near the top E E. 

The water coming from the boiler and passing the 
stop-cock G, makes its exit through the openings 
E E ; at this point the steam is liberated from the 
water and escapes through the openings //, the 
water falls into the cylinder A, passes through the 
opening C, and rises to the water level s s s s in both 
cylinders. D is an overflow pipe to carry off the 
surplus water, and to keep up a sufficient current to 
maintain the water to be tested at the required tem- 
perature. By turning the stop-cock H, both cylinders 
can be discharged. 

This instrument aflfords a ready means of drawing 
water from a steam boiler under any pressure and 
temperature, without ebullition in the cyhnder B, or 
oscillation to the hydrometer. 

Now let us consider the quantity of water neces- 
sary to be blown off, to keep the water in the boiler 
at a certain point of saturation. Suppose the satura- 
tion of the water entering the boiler is ^, and that 
we are maintaining the saturation of water at ^. 
Then, as the saturation of the water is doubled, one- 
half of it must have been evaporated. So, to carry 
the water at ^, as much must be blown out as is 
converted into steam. 

Suppose the required saturation of the water is ^, 
then, since the saturation of the water in the boiler 
is trebled, it must have received 3% from the evapor- 



130 



THE CADET ENGINEER. 



ated water ; so that in this case, we blow off J of the 
water that enters the boiler. 

Similarly, we may show that, 

If required saturation zz 3^, water blown ofFzz-| of 
water entering the boiler. 

If required saturation zz: ^, water blown off 1= | of 
water entering the boiler. 

If required saturation =. ^, water evaporated =1 1 
of water blown off. 

If required saturation nz 1^, water evaporated z= ^ 
of water blown off, etc., etc. 

Besides the practice of blowing to prevent the 
formation of scale, other means are sometimes em- 
ployed, and we will briefly notice a few of them. 

The sulphate of lime causes the most trouble. 
Crushed potato is a mechanical preventive. The 
pulp is supposed to cover the crystals of sulphate of 
lime, and separate them so that they cannot form a 
continuous mass. Chemical preventives are numer- 
ous ; but the great objection to them is, that they 
injure the iron of the boiler. Muriate of ammonia, 
or sal ammoniac, put into the boiler daily, in small 
quantities, acts in the following manner : The car- 
bonate of lime is decomposed, the muriatic acid in 
the sal ammoniac combines with the lime, keeping it 
in solution, and the carbonic acid, uniting with the 
ammonia set free, forms carbonate of ammonia, which 
passes off with the steam. 

But the sal ammoniac has no effect upon the sul- 
phate of lime. 



SATURATION OF WATER IN MARINE BOILERS. 131 

Another remedy for the carbonate of lime incrus- 
tation, is quick-lime. This changes the bicarbonate 
of lime, which is soluble into the insoluble carbonate, 
and this latter can be removed from the boiler at 
such times as are convenient. — 

A preparation of tobacco in the form of a liquid 
has been used in marine boilers. This does not pre- 
vent the "formation of scale, but renders it soft, so 
that it can be swept off or washed away with a stream 
of water from a hose. This has not received a very 
thorough trial, but as far as known it does not injure 
the iron. It is objectionable when the water for use 
on board ship is distilled from the boilers, for the 
liquid also evaporates and gives the water a very 
unpleasant taste. 

Another method of preventing scale, is by the use 
of a compound which removes the saline matter from 
the water before it enters the boiler. This would 
seem to be the best method of all, and the experi- 
ments upon it have been very satisfactory. But for 
some reason it has hitherto failed to be introduced. 

Chloride of barium will prevent the sulphate of 
lime incrustation, and it is said not to have an 
injurious effect upon the iron of a boiler. It is a 
chemical preventive, and decomposes the sulphate of 
lime, forming chloride of lime, which continues in 
solution, and sulphate of barium, a heavy powder, 
which is precipitated as a kind of slush in the bottom 
of the boiler. 

When this preventive is used, and we haul fires 



182 



THE CADET ENGINEEK. 



to clean a boiler, all the water must not be blown 
out before it is cool, or the precipitate will harden. 
When the hand holes are removed, the sulphate of 
barium can readily be cleaned out. 



§ 15. Condensers and Feed Water Heaters. 

In condensing engines, the steam is condensed 
(when it exhausts), either by being brought into 
contact with a jet of cold water, as in the case of a 
common jet condenser, or by passing through or 
around a series of tubes, made cool by water being 
passed around or through them, which is the action 
when a surface condenser is employed. When a jet 
condenser is used, salt water is pumped into the 
boilers ; but a surface condenser, if tight, saves the 
fresh water derived by condensation, and it can be 
returned to the boilers again and again. By this 
means nearly all the feed water is fresh, and but 
little blowing off is required to keep the water at a 
certain point of saturation. A calculation of the 
loss by blowing off will show us the gain derived 
from fresh water condensers, supposing them to be 
tight, and to condense all the steam used by the 
engines. We will show the method of calculating 
the loss by blowing off. 

The number of degrees of heat that must be im- 
parted to the water converted into steam, will be the 
number in the total heat of the steam, minus the 
number of degrees in the feed water. The heat lost 



CONDENSERS AND FEED WATER HEATERS. 133 

by blowing off will be the difference between the 
temperature of the feed water and the sensible heat 
of the steam. A comparison of this loss with the 
entire number of degrees of heat required, being the 
sum of the heat imparted to the steam, and that to 
the water blown off, will give the per cent, of loss. 

Examples. — 1. What is the percent, of loss by 
blowing, where we carry the water at a saturation 
of 3I-, with 20 pounds pressure per steam gauge, the 
feed water having a temperature of 110° ? 

To carry the water at a saturation of ^, twice as 
much is converted into steam as is blown off. 

Sensible heat of the steam =z 260°. 
Total " " " zzll93°.45. 

1193°.45 — 110° = 1083°.45 =: degrees of heat im- 
parted to the water converted into steam. 

But as twice as much water is made into steam as 
is blown off, 

1083°.45 X 2 = 2166°.9 = degrees of heat producing 
useful effect, for every 260° — 110° zz 150° heat lost 
by blowing off. 

2166°.9 + 150° — 2316°.9 — total quantity of heat 
imparted to the water. Therefore, 

(100 X 150°) -~2316°.9zz 6.47 per cent, of heat 
lost by blowing off. 

2. What is the per cent, of heat lost carrying the 
water at ^, the other data being the same as in the 
preceding example ? 



134 



THE CADET ENGINEEK, 



Here only | as much water is converted into steam 
as is blown off, so that 

1083°.45 X f = 812.58 z= heat producing useful 
effect for every 150° lost by blowing off. 

812.58 + 150 = 962°.58, total heat imparted to the 
water. 

(100 X 150°) -r- 962°.58 = 15.58 per cent, of heat 
lost. 

The water that is blown off is sometimes passed 
through heaters, by which the temperature of the 
feed water is increased. By this means there is a 
gain in fuel, as the total quantity of heat imparted 
to the water is not so great as when the temperature 
of the feed water is less. 

Examples. — Find the per cent, of heat saved in 
the two preceding examples, supposing the feed 
water to have a temperature of 160°, instead of 110°. 

1st. When the feed water has a temperature of 
160°, and the saturation is maintained at 3^2? 

(1193°.45 — 160°) X 2 = 2066.9 iz: heat imparted 
to two parts of water converted into steam. 

260° — 160° 1=100° zz heat imparted to one part 
of water blown off. 

2066°.9 + 100° zz 2166.9 = total heat imparted to 
the water. 

2316.9 — 2166°.9 = 150° = gain by use of heater. 

(100 X 150°) -^ 2316.9 z= 6.47 z= per cent of gain. 

2d. When the saturation is maintained at gf , 



A 



CONDENSERS AND FEED WATER HEATERS. 135 

(1193°.45 — 160°) X f = 775.08 = heat imparted 
to I of a part of water made into steam. 

260° — 160° — 100° =: heat imparted to one part 
of water blown off. 

775°.08 + 100° z=875°.08 in total heat imparted 
to the water. 

962°.58 — 875°.08 = 87°.5z=gain by use of heater. 

(100 X 87°. 5) -7- 962°.58 zz 9.09 m per cent, of gain. 

In practice the gain by the use of surface con- 
densers is not as large as the theoretical result. 
Nearly all such condensers leak to some extent, so 
that salt water mingles with the water of condensa- 
tion. Moreover, all the water that is evaporated by 
the boilers is not preserved in the condenser, so that 
a salt feed is necessary from time to time. Surface 
condensers are also much heavier, and occupy about 
twice as much room as the old jet condensers. Their 
first cost, and the numerous repairs they require, 
must be considered. The vacuum also is not gener- 
ally as good as that produced with jet condensers. 
It has been found too that surface condensers have a 
powerful influence in causing the corrosion of boilers. 
Still, with all these drawbacks, the advantages of 
surface condensers have been considered so great, that 
they have been largely introduced. The most suc- 
cessful types have been Pirrson's and Se well's. In 
Pirrson's condenser the exhaust steam passes through 
a number of tubes, and is condensed by a shower of 
cold water around the tubes. There are two pumps. 



136 



THE CADET ENGINEER. 



one for the condensed, and the other for the injection 
water, so that there is a vacuum, both within and 
without the tubes. There is a communication between 
the fresh and salt water sides, so that the vacuum is 
the same in each. The tubes of this condenser are 
secured to one tube head, but pass through the other 
one, which is double, with a rubber diaphragm 
between the two parts. By this means each tube 
is allowed to expand and contract without causing 
leaks. 

Se well's condenser is represented in Fig. 45. The 




CONDENSERS AND FEED WATER HEATERS. 137 

air pump is double-acting, and has two sets of foot 
and delivery valves, one set being for the injection, 
and the other for the condensed water. The in- 
jection water enters at the opening A, is drawn 
through the foot valves hcd, and forced through the 
delivery valves B, through the tubes C, and over- 
board through the outboard delivery D. The exhaust 
steam enters at G, and is condensed by contact with 
the outer surfaces of the tubes. The water of con- 
densation is drawn through the foot valves efg, and 
is forced through the delivery valves H, and the out- 
board I, into a reservoir, from which the feed pumps 
draw their water. There is a loaded valve in this 
reservoir, communicating with the outboard delivery, 
so that, when the reservoir becomes full, the water 
may escape. The openings h i are the ends of a pipe 
connecting the fresh and salt water reservoirs, so 
that any deficiency in the feed water may be supplied 
from the latter reservoir. F is a-n air chamber for 
the salt reservoir, and E is the end of a pipe through 
which the auxiliary pump draws water. The tubes 
in this condenser are not secured to the tube heads, 
but pass through them, and are made tight by rubber 
grummets. By this means each tube is allowed to 
expand and contract independently of all the others. 
Lighthall's patent refrigerator, though not a surface 
condenser, is intended to keep the water in the boilers 
fresh. A common jet condenser is employed, and 
the refrigerator is placed on the side of the vessel. 
By the motion of the ship a stream of cold water is 



188 THE CADET ENGINEER. 

continually passing through a series of long tubes. 
The discharge water passes around these tubes, and 
being cooled is used again for injection water; is 
returned to the refrigerator cooled, and used over 
and over. So if the boilers are filled with fresh 
water when fires are started, the only salt feed 
required will be to supply the water lost by leaks. 

Before leaving the subject of condensers, we will 
consider the amount of injection water required to 
condense steam of a given temperature. The in- 
jection water enters the condenser at a certain tem- 
perature, and coming in contact with the steam, its 
temperature is increased, and that of the steam 
diminished, all the latent heat of the steam being 
made sensible. So we have only to find how large 
a quantity of water will be required to contain all 
the heat in the steam. 

Example. — What is the relation between the in- 
jection water and water of condensation, the total 
heat of the steam entering the condenser being 
1188°. 09, the temperature of the injection water 60°, 
and of the discharge water 110° ? As the water of 
condensation has a temperature of 110°, there are 
1188°.09 — 110 zz 1078°.09 of heat imparted to the 
injection water. But a quantity of injection water, 
equal to the water of condensation, receives 110° — 
60° z= 50° of heat. Hence, the quantity that receives 
1078°.09 of heat will be 1078°.09 -^ 50° =: 21.56 
times the water of condensation. 

When a ship springs a leak, if it is at all serious. 



CONDENSERS AND FEED WATER HEATERS. 139 

the bilge injection is generally used to aid in re- 
moving the water from the hold. We will take an 
example, to show how much may be accomplished in 
this way. 

Example. — How many cubic feet of water could 
be removed from the hold of a vessel by the use of 
the bilge injection, under the following circumstances : 
diameter of cylinder, 60 inches ; length of stroke, 10 
feet ; pressure of steam per gauge, 25 pounds ; revo- 
lutions per minute, 16 ; temperature of water in hold, 
70°; temperature of discharge water, 95°; the steam 
being supposed to follow | of the stroke, and the 
clearance being disregarded ? 

19.635 square feet zz area of piston. 

19.635 X 7.5 =: 145.26 = cubic feet of steam used 
each stroke. 

145.26 X 32 zz 4647.39 zz cubic feet of steam used 
per minute. 

4647.39 X 60 zr 278843.4 zz cubic feet of steam 
used per hour. 

The relative volume of steam and water, at a 
pressure of 25 pounds, is 679, so that 

278843.4 -^ 679 = 410.7 cubic feet of water evapo- 
rated per hour. 

1195°.84 =1 total heat of steam. 

1195°.84 - 95° zz 1100°.84 of heat imparted to 
injection water. 

950 _ 70° zz 25° of heat imparted to one part of 
injection water. 



140 



THE CADET ENGINEER. 



1100°.84 -i- 25° = 44.04, relative quantity of in- 
jection water necessary to produce one part of con- 
densed water. Hence, 

410.7 X 44.04 z= 18087.23 cubic feet of water that 
can be removed from the hold in an hour. 

18087-23 X 62.5 -r- 2240 =: 504.66 tons. 



§16. delation of power (or fuel) and speed in steam 
navigation. 

The resistance experienced by a ship to its motion 
is composed of the resistance of the atmosphere and 
that of the water. The general case of the resist- 
ance of the atmosphere can scarcely be computed, 
on account of the varying circumstances of the 
weather, and the different conditions under which 
the ship is considered, as regards the sail carried. 
The resistance of the water, however, is represented 
by a constant law, increasing as the square of the 
velocity of the vessel. This result is established 
both by experiment and theory. The theory of the 
resistance is, that the particles of water are displaced 
by the vessel with a velocity equal to the ship's 
speed, the power required to displace them varying 
directly as the velocity ; so that the resistance, which 
is the product of the power required to displace the 
water, and the velocity with which it is displaced, 
will vary as the square of the velocity. Thus, if the 
speed of the vessel is 2 knots per hour, the resistance 
is as 4, and if the speed of the vessel is only in- 



EELATION OF POWER AND SPEED. 141 

creased 1 knot, the resistance is as 9. These num- 
bers, it will be understood, only express the relations 
between the resistance offered to the ship at different 
speeds, and not the actual resistance. The resistance 
evidently cannot act on the entire midship section 
of a vessel, else the paddle boards or propeller — the 
area of either of which is very small, as compared 
with the midship section — would not be available. 
The shape of a vessel determines the amount of 
section resisted by the water; and a vessel that moves 
through the water with little displacement of the 
particles, as will be the case if the bow is very sharp, 
will experience less resistance than another vessel 
of the same midship section, but displacing the par- 
ticles of water more abruptly. Still, with a ship of 
a given form, the resistance varies as the square of 
the vessel's velocity. The density of the water also 
has an influence on the resistance. A vessel moving 
through salt water will experience more resistance 
than if the water were fresh, if the immersion is the 
same in both cases. But as salt water is more 
buoyant than fresh water, the immersion of a vessel 
coming from fresh to salt water is diminished, so that 
the resistance to its motion is unaltered. 

To determine the amount of section resisted by 
the water, with vessels of various forms, belongs 
rather to the shipbuilder than the engineer. So we 
will content ourselves with the relations, after the 
form of a vessel is determined. 

We will now consider the power necessary to in- 



142 THE CADET ENGINEEK. 

crease a vessel's velocity. This, as shown both by 
theory and experiment, varies as the cube of the 
velocity. We may explain it in the following manner : 
As the increased speed of the ship requires the speed 
of the engines to be increased in direct proportion 
to the velocity, and as the resistance to be overcome 
varies as the square of the velocity, the power 
developed by the engines, which is the product of 
their speed and the resistance to their motion, varies 
as the cube of the velocity. So, if we make the 
speed of a ship twice what it was originally, the 
resistance will be four times as great, and the power 
required will be eight times that originally employed. 
Now the fuel consumed has a direct relation to the 
power developed, so that we can find the power or 
fuel necessary to increase the speed of a vessel, when 
we know the original conditions. 

Examples. — 1. Suppose a vessel, consuming 25 
tons of coal per day, and developing a power of 500 
horses, has a speed of 9 knots ; what fuel and horse- 
power are required to give the vessel a speed of 11 
knots ? 

According to the law, that the power varies as the 
cube of the velocity, 

9^ : 11^ : : 500 : 912.9, required horse-power. 

Or, 

9^ : 11^ : : 25 : 45.6 tons of coal required per day. 

2. From the fact that it requires such a large in- 
crease of power and fuel for a very slightly augmented 



EELATION OF POWER AND SPEED. 143 

speed, it is evident that we can effect a great saving 
by reducing the speed a httle. This is a matter of 
great importance, and one worthy the attention of 
engineers. 

Suppose we wish to reduce the consumption of 
coal from 30 to 20 tons per day, what will be the 
difference of speedy supposing the vessel to make 12 
knots an hour, when burning 30 tons of coal per 
day ? 

¥oY this case we shall have the proportion : 

30 : 20 : : 12^ : 10.5\ 

Hence the speed will be reduced 1^ knots, or i, 
while we effect a saving in fuel of ^. 

It is found by experiment that large vessels have 
greater speed than small ones, both ships having the 
same model, and each having power proportioned to 
its size. The increase of speed appears to vary as 
the square root of the length of the vessel. Thus, 
if there are two vessels of the same model, one of 
them having four times as much capacity and power 
as the first, and being, therefore, twice as long, the 
speeds of the two ships will vary as the square root 
of 2 to the square root of 1, or the large vessel will 
be If times faster than the small one. But this is 
also a question for shipbuilders, and we will not 
enlarge upon it. 

When steaming against a current, the speed of 
the vessel should be once and a half as great as that 
of the current, so that the vessel may have an effective 



144 



THE CADET ENGINEER. 



speed half as great as that of the current. This 
rule also accords with theory and experiment. If 
we know the velocity of the current, the dijBference 
between that and the speed of the ship will be the 
effective speed. The power required to propel the 
ship will vary as the cube of the actual speed of the 
ship. The power required to propel the ship one 
unit of space, or one knot, will vary as the cube of 
the actual speed, divided by the effectual speed. Our 
object is to make this power as small as possible, and 
we will find it to be so, when the speed of the ship 
is once and a half times that of the current. 

Example. — Suppose there is a current running at 
the rate of 6 knots an hour, opposed to the motion 
of the vessel. What speed should the ship have to 
develop the least power ? 

According to the law, 9 knots should be the speed 
of the ship, but we will try other speeds, and see 
which requires the least power. 

For a speed of 9 knots, 

9 — 6 zz 3 zz effective speed of ship. 

Power required to produce this speed varies as 9^, 
or 729. 

Power required to propel the vessel a distance of 
one knot varies as 729 -^ 3, or as 243. 

For a speed of 10 knots. 

Power required to propel the ship one knot varies 
as 10^ -^ (10 — 6) or as 250. 



MANAGEMANT OF ENGINES AND BOILERS. 145 

For a speed of 11 knots, 

Power required to propel the ship one knot varies 
as ir^ (11 — 6) or as 266.2. 

So we see that the required power continually 
increases for a speed greater than 9 knots. Let us 
try a less speed. 

For a speed of 8 knots, 

Power required to propel the vessel one knot varies 
as 8' -^ (8 — 6) or as 256. 

For a speed of 7 knots, 

Power required varies as 7^-^ (7 — 6) or as 343. 

Hence we see that the law enunciated before holds 
good in giving us the most economical speed for 
steaming against a current. 

§ 17. Management of Engines and Boilers at Sea, 

After the engines, boilers, and their attachments 
have been placed in a vessel, and the ship has been 
accepted from the contractors, the duties of the 
engineer commence. He is expected, as far as pos- 
sible, to keep the machinery in proper condition, and 
to use every available means to make necessary 
repairs. The old adage, "A stitch in time," is very 
applicable in this case. There have been cases 
w^here, by the negligence of an engineer in not 
securing a nut in its position, cross heads and cylinder 
covers have been broken. 

While it is impossible for any one to enumerate 

10 



146 



THE CADET ENGINEER. 



all the things that require an engineer's attention, 
we may note down a few of the most important. So 
let us go on board the vessel, get up steam, and make 
a passage. 

If the boilers are new, we shall probably find a 
quantity of bolts and rivets in the legs. As many 
as possible of these should be removed before the 
boilers are filled. At all events, be the boilers new 
or old, the braces should be examined, to see if they 
are properly set up, and that no brace pins are left 
out. The man and hand-hole plates should then be 
put on, the safety-valve raised, and the boilers filled 
with water. If the water line of the boilers is below 
that of the vessel, by opening the bottom blow, the 
water will enter ; otherwise the hand pump must be 
used. (The safety-valve is raised before filling the 
boiler, to let the air escape as the water enters.) 

Before wooding the furnaces, a thin layer of coal 
should be thrown over the grate bars, or at any rate 
over the back bars. The wood is then put in, and 
at the mouth of the furnaces should be placed all 
the oily waste that has been used for cleaning pur- 
poses. We are now ready to raise steam whenever 
required, as far as the boilers are concerned. 

Let us turn our attention to the engines. All 
keys, glands, and set screws should be carefully ex- 
amined, to see if they are properly adjusted. All 
tools, blocks of wood, etc., that have been used around 
the engines, should be put away. Wicks should be 
put in all the oil cups, unless glass syphons (which 



MANAGEMENT OF ENGINES AND BOILERS. U7 

of late have been much used to supply oil to the 
journals) are employed. The finished work of the 
engines, except such as can readily be cleaned when 
under way, should then be covered with a mixture 
of white lead and tallow, in the proportion of 3 parts 
of tallow to 1 of white lead. 

When the order is given to raise steam, the fires 
should be started, and allowed to burn at a moderate 
rate, and at least three hours should be occupied 
before steam is generated. When the fires are forced, 
there is great danger of injuring the steam chimney 
and other parts of the boiler above the water level, 
for it must be remembered that there is nothing but 
air surrounding these parts before steam is raised. 
It is a good rule not to spread the fires until steam 
commences to form. 

The safety-valve should be kept open until steam 
begins to escape, so that the air may be expelled 
from the boiler. As soon as steam is generated, 
lower the safety-valve, and when there is a snfficient 
pressure, proceed to warm the engines. (The stop 
valves may be opened, either before starting fires, or 
when steam is raised.) To do this, open the out- 
board deliveries and the sea valves, work the pistons 
back and forth a few times by means of the pass- 
over valves, starting bar, or links, as the case may 
be, and then let the engines make a few revolutions, 
opening the injection valves for the purpose of pro- 
ducing a vacuum, and freeing the cylinders of water 
by means of the water valves, when these are fitted. 



148 THE CADET ENGINEER. 

If everything appears to work well, stop the engines, 
feed all the oil cups ; and the engines are ready for 
operation. 

When the engines are in motion, the first care of 
the engineer should be for the boilers, to see that 
the water is carried in them at a proper height ; that 
the required pressure of steam is maintained; and 
that the density of the water does not go beyond a 
given point. For these purposes, spring and syphon 
steam gauges, gauge or test cocks, glass gauges, and 
salinometers are provided. As regards the quantity 
of water in the boilers, too much reliance should not 
be placed on the glass gauges, but the gauge cocks 
should be frequently opened. It often happens that 
glass gauges become stopped up, or the cocks con- 
necting them with the boilers are accidentally shut, 
so that it may be very dangerous to trust to them. 
They are usually so arranged that they can be blown 
through and cleared, and it is well for each engineer, 
when coming on watch, to blow them through, and 
assure himself that they are in working order. 

To keep down the saturation of the water, a 
portion must be blown off, either at certain intervals 
or continuously. The latter method is the best, 
since the saturation can be kept at one point, instead 
of varying, as it must do, if we only blow at intervals. 
The saturation should be tested at least once an 
hour. It is a good plan to keep up a constant circu- 
lation of water in the salinometer pots, so that we 
have only to glance at the salinometer, and we can 



MAJ^'AGEMBNT OF ENGINES AND BOILERS. 149 

ascertain the saturation as readily as we can find the 
height of water in the boilers. 

To maintain the required pressure of steam, we 
are, in a great measure, dependent on the firemen. 
Every minute that a furnace door is kept open is of 
great consequence ; so that quickness is a most im- 
portant characteristic of a good fireman. 

Experience in firing is undoubtedly the best 
teacher, but a few general remarks may not be out 
of place. 

From eight to twelve hours after fires have been 
started, it becomes necessary to clean them, other- 
wise the clinker and ashes will accumulate in the 
furnaces, putting out the fires. When fires are 
cleaned, it takes from fifteen to twenty minutes for 
them to burn up ; so that only one fire should be 
cleaned at a time, and not more than one-third of 
the entire number in a four-hour watch. By this 
means each fire will be cleaned every twelve hours, 
which is sufficient when using coal of fair quality. 
But to the operation. The fireman, after providing 
himself with the necessary tools, deposits a quantity 
of ashes in front of the furnace, pushes the fire back 
or to one side, removes the clinker from the grate 
bars, and with a hoe draws it, together with the 
ashes, out of the furnace. For pulUng out very large 
pieces of clinker, a rake is often used. The fireman 
then pulls the fire forward, or pushes it to the other 
side of the furnace, and removes the rest of the 
clinker and ashes. The fire remaining in the furnace 



150 THE CADET ENaiNEER. 

is now levelled and covered with coal. It is evident 
that the more quickly this operation can be per- 
formed, the less will it affect the pressure of the 
steam. A very reprehensible practice is generally 
resorted to, to protect the fireman from the heat. A 
stream of water is turned on to the dirt and clinker 
as they are drawn from the furnace. This water at 
first forms steam, and drives the fireman away from 
the furnace, thereby causing the door to be kept open 
longer than it otherwise would. Moreover, the water 
has a very injurious effect upon the legs and ash 
pans. If, as the dirt is drawn from the furnace, one 
of the men throws dead ashes upon it, it will be 
smothered, and can be wet down when the fire is 
cleaned. 

Firemen, unless prevented, are in the habit of 
letting the fires burn too low before cleaning them, 
for the reason that the operation can be performed 
much more easily. But when such a fire is cleaned, 
it will nearly go out, and a long time will elapse 
before it will be effective. 

The fires, to produce the greatest effect in making 
steam, should not be more than eight inches in thick- 
ness. No two furnaces should be fired at the same 
time, and, generally, no two furnace doors should be 
open at the same time. The fires should be kept 
bright underneath, all the ashes being removed by 
means of the pricker. No pieces of coal should be 
put into the furnaces that are larger than a three 
inch cube. 



MANAGEMENT OF ENGINES AND BOILERS. 151 

All the ashes should be hoisted before the end of 
the watch, and a reasonable quantity of coal left on 
the floor for the relief 

Boilers with little steam room, or with heating 
surfaces so arranged that steam cannot readily escape, 
are very liable to foam. In the first case the agita- 
tion or hfting of the water seems to be caused by its 
having a greater temperature than the steam, and in 
the second case the water appears to be carried up 
mechanically with the steam, as it rises to the surface. 
All boilers are apt to foam when there is mud or dirt 
of a mucilaginous nature in the water. Changing 
the water in a boiler from salt to fresh, or from fresh 
to salt, is also a frequent occasion of foaming. So 
this is an occurrence for which the engineer must be 
on his guard. Foaming is made evident by the boil- 
ing up of the water in the glass gauge, and by its 
issuing from the gauge cocks as a mixture of steam 
and water. In cases of violent foaming, the water 
will be carried over into the cylinders, which will be 
made evident by the thumping at each end of the 
stroke, and by the breaking down of the engines, if 
the water is not blown out. 

When this foaming occurs, it is desirable to change 
the water in the boilers, and make it all of one kind, 
either salt or fresh, as quickly as possible. So w^e 
should put on a strong feed and blow, and also par- 
tially close the throttle to check the agitation of the 
water. As the water has a greater temperature than 
the steam, it is sometimes advisable to open the 



152 THE CADET ENGINEER. 

furnace and connection doors. By the employment 
of these means, foaming can be soon suppressed in 
well-proportioned boilers. 

Foaming is sometimes caused by having too much 
water in the boiler, whereby the steam room is re- 
duced. So this should be guarded against. 

In boilers with insufficient steam room, foaming 
cannot be entirely suppressed, except by mechanical 
means — such as dry pipes, diaphragms, and the like. 
But by working the steam expansively and throttling, 
much of the foaming may be stopped. Where boilers 
only lift the water, but do not carry it into the 
cylinders, the only remedy seems to be to close the 
throttle almost entirely, at short intervals, so that 
the actual height of the water can be ascertained. 

Should the water in a boiler get low by accident, 
and the engineer is in doubt as to its condition, no 
time should be lost in hauling fires, closing the stop 
valve of that boiler, and shutting the valve by which 
the water is escaping. In such a case the feed should 
not be put on, as it may lead to fatal consequences. 
After a sufficient time has elapsed for the boiler to 
cool, water may be admitted and fires started once 
more. 

Should a tube burst in a vertical tubular boiler, 
and leak to a serious extent, fires must be hauled 
from that boiler, the stop-valve closed, the water 
blown out, and the boiler entered to plug the tube. 
After the tube is found, we have only to drive a pine 
plug into each end. The greatest trouble is to find 



MANAGEMENT OF ENGINES AND BOILERS. 153 

the tube. A tolerably eflfectual way of making the 
discovery is as follows : stop up the front and back 
ends of the tube box for a height of three or four 
inches, and fill this space with water. Then, by 
looking into the boiler, we can see if there are any 
leaks in the lower ends of the tubes. A leak in the 
top of a tube can generally be found, when there is 
water in the boiler, by putting a lamp or a piece of 
waste saturated with turpentine between the tubes 
near the upper tube sheet. 

Should it be a horizontal tube that requires to be 
plugged, it can readily be seen at the front end, and 
can be stopped with a pine plug. To stop the leak 
in the back connection, the fire under the tube box 
that contains the faulty tube must be hauled, so that 
the back connection can be entered, and the tube 
plugged. This is rather warm work, but it can be 
done. An iron plug should be used for the back end 
of the tube. 

If all the fires in a boiler are hauled to plug up a 
horizontal tube, a long bolt and cup washers should 
be used. A pine plug should be driven into each 
end of the tube, with a hole through the centre for 
the long bolt to enter. The cup washers should then 
be put on, the space between them and the plugs 
filled with cement, and the nuts on each end of the 
bolt screwed up. 

Should a rupture take place in the boiler, if it is 
not in the fire surface, and can be reached, it may 
be temporarily stopped by driving in a pine plug. 



154 THE CADET ENGINEER. 

Otherwise, if it causes a dangerous leak, fires must 
be hauled until it can be repaired. But if the ship 
is on a lee shore, where the consequences of hauling 
the fires might be fatal, the fire must be hauled from 
the leaking furnace, and the steam worked off (so 
that the engine is running on a partial vacuum), 
when the leak can soon be stopped by shoring up a 
patch against the hole. The patch can be a piece 
of board, or anything that is convenient, for we will 
fill up that furnace with ashes, and throw it out of 
use. When this is done, the boiler is ready for steam 
again. 

Having now noted down the principal duties of 
the engineer, as regards the boilers, let us turn our 
attention to the engines. When the engines are 
under way, the engineer should see that a proper 
amount of water is supplied to the condenser, so that 
the discharge water is kept at the required tempera- 
ture, the proper vacuum maintained, and that the 
air-pump is not overloaded. A vacuum gauge is 
usually provided, and also a thermometer to indicate 
the temperature of the water in the hot well. The 
chief attention of the engineer, after the care of the 
boilers, should be given to the bearings. If the 
engines are in line, and the bearings are properly 
constructed, they will not heat, except by negligence. 
They should receive special attention when the 
engines are started, since that is the time that they 
are most liable to heat. As soon as a bearing shows 
signs of heating, a plentiful application of oil and 



MANAGEMENT OF ENGINES AND BOILEKS. 155 

sulphur, or black or white lead and oil, will generally 
cool it. Should these means fail, water must be used, 
but it should be the last resort. 

While the general duties of the engineer are very 
plain, it is impossible for any one to enumerate the 
thousand and one things that may occur, and the 
remedy suitable for each. Neither would such a 
course be advisable, for in an emergency it would be 
ludicrous, were not the consequences so disastrous, 
to see an engineer, book in hand, looking for the 
particular break down. Without doubt experience 
is a most valuable assistant, but presence of mind 
and sound common sense are also important adjuncts. 

Should a water-pipe burst, it may be temporarily 
repaired by wrapping canvas, in strips about one inch 
wide, around it, securing the canvas by marline, the 
pipe being first covered with red-lead putty. If the 
pipe is very much worn, a piece of copper should be 
bent around it before it is wrapped, so as to increase 
the strength. 

Feed pumps sometimes refuse to work by reason 
of the safety-feed being caught up, or insufficiently 
weighted. This should be examined as soon as a 
pump refuses to feed. If the feed water is very hot, 
vapor forms in the pump barrel, and the receiving 
valve cannot open. When this is the case, if there 
is no vapor valve fitted to the pump, it is well to 
slack up the gland of the stuffing box, so that the 
vapor can escape. Where surface condensers are 
employed, and tallow is used for lubricating the 



156 THE CADET ENGINEER. 

cylinders, hard lumps of tallow frequently get into 
the pumps, and prevent their working. (The tallow 
also gets into the channel ways of the condenser, 
and it should not be used, except when absolutely 
necessary, and then very sparingly if a steamer has 
surface condensers.) Bilge pumps and auxiliary 
feed pumps sometimes will not draw water from the 
bilge for want of being charged. This can be effected, 
in the case of the auxiliary pumps, by letting them 
pump from one sea-cock to another. If, after they 
are charged, they still refuse to pump out the bilge, 
it is probably because the strainers are stopped up. 
The auxiliary pumps of a steamer should never be 
used to pump out the bilge, except in case of a 
dangerous leak; otherwise, they cannot be kept 
efficient. 

Should the vacuum become impaired, all the glands 
of the stuffing boxes of the piston and air-pump rods, 
and of the expansion joints of the exhaust pipes, 
should be set up. We can ascertain their tightness 
by holding a light near them, and observing whether 
the flame is drawn in. If all the joints and stuffing 
boxes are tight, it is probable that the diminution in 
vacuum is caused by an insufficient supply of injection 
water ; otherwise, there must be some derangement 
of the foot or delivery valves. 

The condenser sometimes gets hot for want of a 
sufficient supply of injection water. The practice 
of letting a stream of cold water on to the condenser 
is an unskilful mode of cooling it. A much better 



MANAGEMENT OF ENGINES AND BOILERS. 157 

way is to open the bilge injection, leaving the sea 
injection cock also open. The vapor and steam will 
then escape from the condenser into the bilge, and 
in a few minutes the condenser will take the injection 
water again. As soon as the vacuum is restored, 
close the bilge injection. 

In making a very long run it sometimes happens 
that the connections and flues require cleaning. In 
this case they can be swept without stopping the 
engines, one boiler at a time. 

The engineer should keep a note book, in which 
he may put down, from time to time, such things as 
will need attention, when there is a chance to make 
repairs. By this means the labors of overhauling 
are systematized and made much easier. 

If there is an accumulation of salt in any of the 
tube boxes, caused by leaky tubes, it may be cleared 
away by attaching a hose to the boiler, above the 
water level, and letting steam on to the salt. 

The following cases are noted down, to show what 
may be done in an emergency with limited facilities. 

Should the stem of a double puppet valve break 
between the two halves of the valve, both halves 
might continue to rise and seat for a few revolutions, 
the lower half being forced up by the pressure of 
the steam, and the upper half being raised by the 
lifting rod. But in seating the lower half would be 
apt to cant, so that the upper one could not seat 
fairly. Then the steam port would be partially open 
all the time, and this would be indicated by the 



158 THE CADET ENGINEER. 

heating of the condenser and the sound of wire 
drawing steam. Such a position of affairs is not a 
very pleasant one, when a steamer with a single 
engine is in the middle of the ocean. As such a 
case actually occurred, it may be interesting to state 
the method employed to remedy the difficulty. The 
engine was stopped, the stop-valve of the boiler 
closed, and the steam blown off. The bonnet of the 
steam-chest was then removed, and the lower half 
of the valve secured in its seat by iron props, and 
the jagged edges of the broken stem cut off; the 
bonnet was replaced, arid the operation was complete 
— the whole thing occupying a little more than an 
hour. 

In the fall of 1862 the U. S. Steamer "Susque- 
hanna" went on a trial trip in Pensacola Bay, and 
performed very satisfactorily. Just as she was coming 
to anchor, a dense volume of steam was observed to 
issue from the starboard cylinder. On removing the 
lagging, it was found that the cylinder had a crack 
extending from the bottom flange upward, a distance 
of a little more than eight feet, in the direction of 
the axis. Most engineers would have considered 
this too serious a break down to be repaired on board 
ship, and would have called for a survey. But the 
chief engineer, Mr. George Sewell, determined to 
patch the crack, and strengthen the cylinder by 
bands. The patches were riveted on, the rivets 
being driven from the inside of the cylinder, and 
having their heads countersunk. Bands of nearly 



MANAGEMENT OF ENGINES AND BOILERS. 159 

the right size were found among the ruins of the 
navy-yard, having formerly done duty as tires of the 
wheels of ox carts. They had to be put around the 
cylinder in two pieces, and then riveted together by 
a piece lapping over the ends, to avoid cutting the 
frame for the introduction of the lugs. When the 
patching and banding were completed, the edges of 
the crack were peaned together, and the leakage of 
steam was imperceptible. But there were more diffi- 
culties to be overcome. The cylinder was so thin 
in many places that it had assumed an elliptical 
shape, there being a difference of a quarter of an 
inch between two diameters at right angles to each 
other. The piston rod was also sprung about a 
quarter of an inch, and had canted the piston, so 
that it was not at right angles to the axis of the 
cylinder. The piston rod gave abundant evidence 
of its condition by the steam leaking through the 
stuflQng box with a sound like that of a steam 
whistle. • To remedy this, an external stuffing box 
was constructed, which worked very well. A ring 
was made, in two pieces, fitting the piston rod, and 
having lugs which were secured to the stuffing box 
bolts, keeping the ring about four inches away from 
the stuffing box. Hemp packing was tightly wound 
around the rod, and thus but little steam escaped. 
Now for the cylinder. This was planed out, the 
piston rings serving as cutters. Steel packing rings, 
tempered and with a cutting edge, were used, being 
set out quite hard. The engines were made to move 



160 



THE CADET ENGINEER. 



very slowly, for several hours at a time, until the 
condition of the cylinder was much improved. 

This may not seem to be any great piece of 
engineering, and, doubtless, in a shop it would be 
but little thought of The reader must remember, 
however, that it was accomplished with the facilities 
on board the vessel, and this may cause him to view 
the matter in another light. 

During the latter part of 1862, while one of the 
authors of this work was attached to the U. S. 
Steamer "Iroquois," a serious accident occurred on 
the passage from the Kio Grande to Pensacola. The 
plunger of the air-pump, which had worn away at 
the centre so that the diameter was diminished seven- 
eighths of an inch, had such an uneven motion that 
the stud-bolts securing the packing gland were 
carried away. The gland, becoming detached, fell 
between the end of the plunger and the air-pump 
bonnet, breaking both the gland and bonnet in an 
irreparable manner, and cracking the channel ways 
in several places to a very serious extent. 

The engines were immediately stopped, and prepa- 
rations made to repair damages. The air-pump was 
double-acting, having a set of foot and delivery valves 
on each side of the plunger. The foot and delivery 
valves on the same side of the plunger as that to 
which the gland was bolted were removed, and the 
openings stopped up by bolting pieces of board to the 
seats. The broken stud-bolts which secured the 
gland were drilled out, and new ones substituted. 



OVERHAULING ENGINES AND BOILERS. 161 

A new gland was made of wood, with a sheet-iron 
ring behind it to prevent the wood from tearing 
away. The broken pieces of the channel ways were 
replaced with putty and boards behind them, the 
boards being secured by jacks and shores from the 
ship's side. The cracks were stopped from the inside 
with putty, waste, and wedges. The communication 
valve between the fresh and salt water pumps was 
opened, and the repairs were complete. 

The salt water pump, of course, worked single- 
acting, and the fresh water pump acted as an 
additional air-pump, so that salt water was supplied 
to the boilers. In this condition the " Iroquois" com- 
pleted her trip to Pensacola, and from thence pro- 
ceeded to New York, making a very fair passage. 
The whole repairs were made in twenty-four hours. 

We might continue giving accounts of break downs 
and their remedies to an almost unlimited extent, 
but every engineer of much experience has a budget 
of such narrations. We must crave pardon for in- 
troducing the casualties that were of peculiar interest 
to ourselves, from the fact of our being present at 
their occurrence. 

§ 18. Overhauling the Engines and Boilers in port. 

When a ship arrives in port, and the anchor is 
down, if it is the intention to stay but a few hours, 
it is advisable to bank the fires. They should be 

first cleaned, and then pushed back, so as to. leave 

11 



162 



THE CADET ENGINEER. 



the front grate-bars bare. By this means the engineer 
has control of the steam, and avoids the nuisance 
of blowing off, while, with fifteen minutes' notice, 
he can spread the fires, and be ready to get under- 
way. 

In these few hours a good engineer will avail him- 
self of the opportunity of making such temporary 
repairs and adjustments as are necessary, and there 
is always something to do when an engine is 
stopped. 

Should it be decided that the ship is to remain in 
port for several days, as soon as she is properly 
secured, and the engines are no longer needed, the 
sea-cocks and outboard delivery valves should be 
closed, fires hauled, and the water blown out of the 
boilers down to the crown sheets. After the boiler 
is cool, the remaining water can be pumped out by 
the hand pump, or run into the bilge. (It is confi- 
dently asserted that a large proportion of the ills 
that boilers are heir to are caused by a too rapid 
combustion in raising steam, and by blowing the 
water down so low that an unequal contraction takes 
place in the iron. That boilers generally give out 
first in the water bottoms and steam chimneys is 
doubtless the result of these two circumstances.) As 
soon as fires are hauled, the work of cleaning the 
engines should commence. The wicks should be 
removed from all the oil cups, the oil emptied out, 
and the cups thoroughly cleaned inside. The covers 
should then be put on, and if there are still any 



OVERHAULING ENGINES AND BOILERS. 163 

openings where dirt may get upon the journals, they 
should be stopped up with waste or tallow. All the 
white lead should be removed from the bright work, 
and all the dirt and grease around the engines 
cleaned off. Potash is frequently used for this pur- 
pose, being dissolved in warm water, and applied 
with a mop. It is then washed off with cold water, 
and the work only needs to be dried, for all the 
white lead and grease will be removed. After the 
engines are cleaned, if the boilers are cool, the flues 
or tubes and connections should be swept, the ash 
pits and furnaces cleaned out, and all the dirt sent 
up. The bilge should also be thoroughly cleaned 
and whitewashed. 

After the whole engine department has been pro- 
perly cleaned, the men should be divided into gangs 
to repair and scale the boilers and overhaul the 
engines. And here the advantage of system is at 
once apparent. The engineer is not expected to 
work, but only to find brains for those who do. And 
it is astonishing how much more work some engineers 
can get done in a given time than others. The one 
who thinks of what he will need when he raises his 
cylinder covers, for instance, and has the falls, slings, 
blocks, wire for the nuts, and the like, at hand, will 
certainly get along faster than if he had to wait for 
a sling, to get a saw to cut the blocks the proper 
length, etc. But this is a thing that every engineer 
must learn for himself. 

Let us first superintend the gang of men that are 



164 



THE CADET ENGINEER. 



working around the boilers. To scale a boiler is not 
the work of a few hours, as some have represented 
it, but, particularly in the case of tubular boilers, is 
a long and tedious operation, sometimes requiring 
two or three weeks. The crown sheets and flat 
surfaces can be scaled by means of hammers ground 
to an edge at each end. Parts not readily accessible 
can sometimes be scaled by means of long scaling 
bars, sharpened at the ends. The tubes, however, 
cannot be scaled in this way. In a vertical water- 
tube boiler we must ream the scale out of the tubes 
with suitable tools, and if the scale is over Jg of an 
inch in thickness, two men can rarely scale more 
than thirty or forty tubes per day. Fig. 46 shows 




two styles of tools for vertical tubes, both of which 
work very well. 



OVERHAULING ENGINES AND BOILERS. 165 

In the first tool the collar A, on the rod, is made 
about y^g of an inch less in diameter than the inside 
diameter of the tube. Just above the collar the rod 
is spUt, and the two pieces are bent to a width equal 
to the diameter of the collar. These two halves of 
the rod form the cutters, and are made perfectly 
rigid. The second tool has two cutters, C and D, at 
right angles to each other, and with a length equal 
to the diameter of the collar. The cutters have 
rectangular faces, and by being locked into each 
other are both on the same level in the rod. They 
are held in place by the key E. 

In a horizontal, tubular boiler it is impossible to 
scale the tubes effectually, and all such plans as 
burning a train of shavings and the like are more 
visionary than real. All that we can do is to knock 
off as much as possible by means of chisel bars, and 
by passing flat bars of iron or steel between the 
tubes, and tapping them lightly. When time will 
permit, in scaling these boilers, it is a good plan to 
leave the water in the boilers, and only let it run 
down below the row of tubes that are to be scaled, 
for the scale will be much softer than if the atmos- 
phere comes in contact with it. 

While the boilers are being scaled, the other 
necessary repairs should be going on. The check 
and blow valves should be examined, scraped if 
necessary, and their stems repacked. All plug-cocks 
should also be overhauled, and made tight by scraping, 
if possible ; if not, by grinding with a little emery 



166 



THE CADET ENGINEER. 



or ground glass. Before the plugs are put in again, 
they should be rubbed with black lead and tallow. 
The safety and stop valves should also be examined, 
and made to work freely. 

Should the boilers require patching, a hard patch 
is preferable, if the leak is in the fire surface, other- 
wise a soft patch will answer. A hard patch is made 
by cutting out the defective iron and riveting on a 
patch, which can be chipped and caulked. Where 
it is impossible to hold the rivets for a hard patch, 
what is called a locomotive patch may be substituted. 
Here tap-bolts with heads like those of countersunk 
rivets, and a square shoulder to screw them into 
place, are used. The holes in the patch are counter- 
sunk, and the bolts are tapped into the boiler, the 
square shoulder being twisted off. The patch can 
then be chipped and caulked like a hard patch. 
The defective part is first cut away before putting 
on this patch. 

The seams of some boilers, instead of being chipped 
and caulked, are split-caulked. But this is a cheap 
mode of construction, and should not be resorted to. 

When there are no facilities for putting on a hard 
patch, or time will not permit, we must substitute a 
soft patch. In this case we do not cut out the de- 
fective part of the iron, but, after taking a piece of 
sheet lead and making a template, we turn a patch 
by it, putting a lip all around the edges to hold 
cement. The holes for the bolts are generally first 
cut or drilled in the boiler, and their position is 



OVERHAULING ENGINES AND BOILERS. 167 

transferred to the patch by a stick with white lead 
on the end, which we put through the holes in the 
boiler, and press against the patch. When all the 
holes are made, the patch should be bolted to its 
place, and accurately fitted. It should then be taken 
oflf, a quantity of cement put on the inside, and be 
put on again to stay. The cement is composed of 
red and white lead, and fine iron borings, made as 
stiff as possible. Grummets, made of wicking covered 
with cement, should be put under the heads of the 
bolts, also washers under the nuts. Sometimes it is 
a diflBcult matter to get the bolts through the holes, 
when a method called wiring or fishing them must 
be resorted to. A wire is run through the hole 
which we wish the bolt to enter, until it can be con- 
veniently reached, the bolt already grummeted is 
attached to it, and can be drawn into its proper 
place. Sometimes a slender rod, split at one end, 
which grips the bolt, is employed. 

A soft patch on a fire surface should not be made 
of iron more than -^^ of an inch in thickness. If 
the leak is not a very large one, it is well to cut 
some holes, so as to let the water in the boiler have 
free access to the patch. When so fitted, a soft 
patch in a furnace will frequently last for several 
months. 

A short crack in the iron of the boiler may fre- 
quently be made tight by driving rivets along it, and 
caulking the heads well. 

While in port, tubes that have been plugged up 



168 THE CADET ENGINEER. 

should be cut out, and new ones inserted. The 
leaking tube is first cut clear of the tube sheets, and 
a long bolt is introduced into it, with a washer at 
one end, that will just go through the hole in the 
tube sheet. The other end of the bolt passes through 
a crowfoot resting against the other tube sheet, and, 
by screwing up the nut on this end of the bolt, the 
tube is drawn clear of one tube sheet. It can then 
be readily worked out the rest of the way, unless 
there is a very thick scale on it, when the operation 
is somewhat tedious. After the old tube is removed, 
the holes in the tube sheets should be filed smooth, 
if there are any irregularities in them. The new 
tube should not project more than | of an inch 
beyond each tube sheet before it is expanded. Being 
put into its place, one end of the tube is hammered 
over, and the expanding tool is driven in. The 
same operation is then repeated at the other end. 
In the case of horizontal tubes, one expanding tool 
will answer for both ends. But vertical tubes require 
two, a top tool and a bottom one. In expanding the 
lower end of a vertical tube, one man enters the 
boiler underneath the lower tube sheet, and holds 
the expanding tool in its place, while another man 
drives the mandril (which passes through the tube) 
from the upper tube sheet. 

Sometimes old tubes that leak at the tube sheets 
can be made tight by being caulked or re-expanded. 
For caulking the ends of the tubes a boot tool (so 
called from its resemblance to a high-heeled boot) is 



OVERHAULING ENGINES AND BOILERS. 



169 



often used, but a small, round-faced hammer will 
answer every purpose. If neither caulking nor ex- 
panding will make a tube tight, a ferule or thimble 
may often be driven in with very good effect. Fig. 
47 is a sketch of Clark's patent thimble, which is 
very highly spoken of. 

The ferule, it will be seen, is in two pieces. The 
inner piece is usually coated 
with red lead putty, and 
when the outer piece is 
driven up, the tube is ex- 
panded, and the leak 
stopped. 

In overhauling the 
boilers, all the braces and 
pins should be examined. 
When any pins are found 
to be loose by corrosion, they should be removed, 
and larger ones put in. All the braces should be 
sounded with a hammer, and those that are loose 
upset, and made of the proper length, so as to take 
their share of the strain. 

The bottoms of the boilers should be painted, and 
for this purpose the following is a most excellent 
preparation : 




Red Lead, 50 pounds. 
Venetian Red, 12 " 
Whiting, 5 " 

Litharge, 



91 



170 THE CADET ENGINEEK. 

Grind the ingredients in a paint mill, with boiled 
linseed oil. Then mix the preparation with boiled 
linseed oil to proper consistency for painting. 

In putting on the hand and manhole plates, great 
care is often necessary, particularly in the case of 
old boilers. The iron around the hole is often cor- 
roded by the use of rubber gaskets, as they con- 
tain a large quantity of sulphur and zinc, which 
accounts for their action. By covering rubber gaskets 
with black lead and tallow, every time the plates are 
put on, injury to the iron may be, in a great measure, 
prevented. Where we cannot make a plate tight by 
employing a rubber gasket, a gasket of hemp pack- 
ing, saturated with tallow, will frequently have the 
desired effect. 

While the work of overhauling the boilers is pro- 
gressing, the examination and repair of the engines 
should be going on. The cylinders and pistons 
should be looked at, to see if they are in good con- 
dition, if the rings fit closely to the cylinders, and 
if the springs require setting up. The pistons should 
have all the dirt removed from the inside before the 
followers are replaced. The foot and delivery valves 
should be examined, also the air-pump plungers or 
buckets, which should be repacked, if they require it. 
All stuffing boxes that leak should be repacked, and 
all leaky joints made anew. Where the keys of a 
bearing are driven home, a liner should be put behind 
one of the brasses, the butt or crown brass, as the 
case may be. 



OVERHAULING ENGINES AND BOILERS. 171 

If any of the bearings have given trouble by heat- 
ing, they should be examined, and the brasses scored. 
But large bearings that have given no trouble should 
not be touched, for it is a correct principle in engineer- 
ing, to " Let well enough alone." 

If any apprehensions are entertained that the 
shaft is out of line, this can be determined approxi- 
mately, in the case of a direct-acting propeller engine, 
by disconnecting the rod at the crank-pin end, swing- 
ing it on the centres and half centres, and measuring 
its distance at each of these points from the crank, 
which we also swing around with the rod. The 
accurate method is to put two straight edges on the 
slides, one at each end; run a line through their 
centre points, and continue it beyond the shaft. Set 
a T square on one of the straight edges, making one 
edge of the blade cut the centre point. Then erect 
a perpendicular to the line we have run, at the centre 
of the shaft, by looking it out of wind with the edge 
of the T square. The distances of the crank, at the 
centres and half centres, from this perpendicular and 
athwartship line are then to be measured, and if they 
vary, the shaft is not in line. In the case of a side- 
wheel steamer, to see whether the shafts are in line 
with each other, we have only to measure the dis- 
tances between the cranks at the centres and half 
centres. 

In packing a large stuffing-box, such as that of a 
slip joint on a steam or exhaust pipe, it is well to put 
a piece of lead pipe, with a strand of hemp packing 



172 THE CADET ENGINEER. 

run through it, in the bottom of the recess. The 
packing for a slip joint should be well saturated with 
black lead and tallow, otherwise it sometimes becomes 
a very difficult matter to remove the gland when 
repacking is necessary. In fact, black lead and tallow, 
or black lead alone, should be put on the faces of all 
joints, all cocks and rubbing surfaces, follower bolts, 
and the like, to prevent corrosion. 

All pipes that have burst, or have holes in them, 
and have been wrapped temporarily, should be re- 
paired in a more permanent manner while in port. 
If hard solder is to be used, the pipe is secured 
together by copper wire, or a patch fitted and wired 
in its place, the surfaces that we design to solder 
having previously been scraped clean. Then apply 
spelter solder and pulverized i)orax, mixed with water. 
Place the pipe in a charcoal or anthracite fire in the 
portable forge, and when the solder melts, the opera- 
tion is completed. Care should be taken not to burn 
the pipe. 

If soft solder is to be used, the pipe should first be 
scraped clean. Then apply a mixture of muriatic 
acid and water (one gill of acid to one and a half of 
water), in which a little zinc has been dissolved. (In 
the absence of the acid, pulverized rosin may be sub- 
stituted.) Then run the solder into the seam with 
a soldering iron, previously tinned. Lamps, oil cans, 
and tinware can be soft soldered in the same way. 



INDEX 



A. 

Page 

Action of the Slide Yalve 108 

Air 63 

Allen and Wells's Cut-off 91 

Analysis of Coal 63 

Analysis of Sea Water 123 

Angle of the Screw 39 

Areas of Chimneys 66 

Area of the Screw's Disc 43 

B. 

Back-acting Engines 12 

Back Pressure 85 

Balanced Slide Yalve 117 

Banking Fires 161 

Best Form of Propeller 41 

Bilge Water Gauge 19 

Blowing Off 129 

Box Yalve 119 

Bristol's Yalve 119 

Broken Condenser and Channel Way 160 

Bursted Feed Pipes 153-172 

Bursted Tubes 167 

(173) 



174 INDEX. 

C. 

Page 

Cam Cut-off 88 

Carbonic Acid 64 

Carbonic Oxide - 64 

Centre of Pressure 26 

Clark's Thimble 169 

Cleaning Boilers 163 

Cleaning Engines and Bilges 162 

Cleaning Fires , . 149 

Combustion 63 

Comparison of Pitches of Propellers 41 

Comparison of Feathering and Eadial Wheels 21 

Condensers 132 

Cornish Yalve 117 

Counter 19 

Cracked Cylinder 158 

D. 

Davies's Yalve 122 

Definition of Steam 73 

Definition of Screw Propeller 37 

Derangement of Feed Pumps 155 

Description of the Indicator 95 

Dickerson's Boiler 16 

Direct-acting Engines 11 

Double Puppet Yalves 117 

Draft 66 

Drag 35 

Duties of an Engineer 145 

Duties to Boilers 148 

Duties to Engines 154 

E. 

Efficiency of Boilers 105 

Engineers' Note Book 157 

Equilibrium Oil Cup 21 

Erection of Engines 69 



INDEX. 175 

Page 

Examining Bearings 170 

Example in Expansion 78 

Expanding Pitch 39 

Expansion Diagram 100 

Expansion of Steam 75 

F. 

Feathering Wheel 22 

Filling the Boilers 146 

Firing 149 

Flue Boiler 14 

Foaming 151 

Fogle's Oil Cup 21 

Friction of an Engine 104 

Friction of Feathering Mechanism. 36 

G. 

Grain by use of Heaters 134 

Gain in Fuel by Expansion 81 

Gain in Mechanical Effect by Expansion 77 

Geared Engines 12 

Generatrix of Propeller 37 

Geometrical Action of the Slide Yalve 110 

Green's Cut-off 93 

H. 

Hauling Fires 162 

Haystack Boiler 15 

Helicoidal Area 57 

High Pressure Diagram 102 

Horizontal Tubular Boiler 14 

Horse-power of a Boiler 105 

Horse-power of an Engine... 102 

How to draw the Curve of Expansion 78 

How to lay down a Propeller 47 

How to measure a Propeller 45 

How to sweep up a Propeller 66 



176 INDEX. 

I. 

Page 

Injection Water required 138 

Impaired Yacuiim 156 

J. 
Joints of Engines 72 

L. 

Lap 110 

Latent Heat of Steam 74 

Lead 110 

Leaks in Boilers 153 

Lighthall's Eefrigerator 137 

Limit to Expansion 85 

Limit to Lap 114 

Lining Holes through Ship's Side 72 

Lining up the Shaft 171 

Link Motion 94 

Long's Salinometer Pot 128 

Loss by Blowing 133 

Loss by Oblique Action 30 

Low Water 152 

M. 

Man and Hand-hole Plates 170 

Manley Wheel 22 

Material for Propellers 57 

Mean Pressure during Expansion 77 

Mechanical Eifect of Expansion 77 

Miscellaneous Kepairs to Boilers 165 

Negative Slip 43 

New Ironsides' Yalve 122 

Number of Blades of Propeller 43 



INDEX. 177 

O. 

Page 

Objection to Feathering Wheels 25 

Oscillating Engines 12 

Overhauling Braces 169 

Overhauling Engines 170 

P. 

Packing large Stuffing-boxes 171 

Paint for Boilers '. 169 

Patching Boilers 166 

Percussion G-auge 18 

Pirrson's Condenser 135 

Pitch of Propeller 38 

Piston Yalve 120 

Porter's Indicator 95 

Properties of Steam 73 

Putting in Tubes 167 

Q. 

Quantity of Water blown ofp 129 

E. 

Eadial Wheel 21 

Eaising Steam 147 

Eelations of Power and Speed 141 

Eepairing leaking Tubes 168 

Eepairing Pipes 172 

Eesistance to a Ship's motion 140 

EoUing Circle 25 

Eoot's Engine 13 

Eotary Engines , 12 

Eotary Yalve 120 



Salinometer 125 

Salt in Tube Boxes 157 

12 



178 INDEX. 

Page 

Scale 124 

Scale Preventives 130 

Scaling Boilers 163 

Scaling Tools 164 

Setting Boilers 71 

Setting Slide Yalves 114 

Sewell's Condenser ... 136 

Sickel's Cut-off 90 

Side Lever Engine 11 

Slide Cut-offs 92 

Slip of Paddle-wheels 33 

Slip of Propeller 42 

Speed of large and small Vessels 143 

Steam and Yacuum Gauges 17 

Steaming against a Current..... 143 

Stephens's Cut-off 90 

Stimer's Boiler 17 

Sweeping Flues under way 157 

System in Overhauling 163 

T. 

Table of Atomic Weights and Volumes 67 

Table of Hyperbolic Logarithms 78 

Table of Initial Pressure 84 

Table of the Properties of Steam 75 

Taking a Diagram 97 

Terminal Pressure of Expanded Steam 77 

Theoretical Curve of Expansion 76 

Theoretical Diagram, and Practical Modification 98 

Thermometer used as a Salinometer 127 

Thrust of Propeller 44 

Trunk Engines 12 

V. 

Vertical Tubular Boiler 14 



INDEX. 179 

W. 

Page 

Waddell's Yalve 121 

WarmiDg the Engines 147 

Water as Fuel 65 

White Leading Bright Work 147 

Winter's Cut-off......... 92 

Wooding Furnaces 146 

Wright's Engine 13 



^ 



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NOVELS OF LIFE AND MANNERS. 
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Paul Clifford 

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New Dictionary of Quotations, 



A New Dictionary of Quotations, from the Greek, Latin, and Modern Languages, 
translated into English, and occasionally accompanied with Illustrations, His- 
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every important word. One vol. crown 8vo., muslin, beveled boards. 



On the score of utility it may be 
classed among the most excellent and 
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rust. The New Dictionary will find a 
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Lieber^s Civil Liberty. 

On Civil Liberty and Self-Government. By Francis Lieber, LL.D., author of 
"Political Ethics," "Principles of Legal and Political Interpretation," etc. etc. 
8vo. 

Jg^^ This work is used as a text-book in our best institutions of learning. 



It is to all intents and purposes a text- 
book of American politics. Would that 
it might be generally regarded as such! 
Then our young men, instead of wast- 
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ing, would be laying up a store of com- 



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would prove of enduring value to them- 
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in what true liberty consists, and would 
recognize the sure means of its perpet- 
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Parsons on Notes and Bills. 

A Treatise on the Law of Promissory >• ^fes and Bills of Exchange, with an 
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relation to Bills, Notes, Letters of Credit, Drafts, Orders, and Checks; to- 
gether with an examination of the questions which the Statute suggests, and 
the English authorities upon those questions which have arisen under the 
English Stamp Acts, and may arise under our own. By Theophilus Parsons, 
LL.D., Professor of Law in Cambridge University. Two vols. 8vo. 

* * * The general character of the 
Treatise is exhaustiveness, the learned 
author having labored with splendid 
success to make his work one that shall 



meet all the requirements of that prov- 
ince of Law to which it is devoted, and 



to give to persons interested therein a 
guide upon which the completest reliance 
can be placed. Its publication adds to 
his high fame, and it places the entire 
business world under the greatest obli- 
gations to him. — Boston Traveller. 



Hilliard on Bankruptcy and Insolvency. 

A Treatise on the Law of Bankruptcy and Insolvency. By Francis Hilliard, 
author of " The Law of Torts," etc. One vol. Svo. 



Mr. Hilliard' s book is evidently the 
result of much intelligent labor, and, as 
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cially since the recent vote of the House 
of Representatives appears, for the pres- 
ent at least, to have settled the question 
of a new and permanent national law of 
bankruptcy. — American Law Register. 



Johnson^ s Lives of the English Poets. 

With Critical Observations on their works. With Notes, by Peter Cunningham, 
and a Life of the Author, by Macaulat. With a portrait on steel. Two vols. 
12mo. 



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Hamilton's History of the United States. 

History of the Republic of the United States of America as traced in the writings 
of Alexander Hamilton and of his cotemporaries. By John C. Hamilton. In 
seven vols. 8vo. (Vol. VII. just published.) 

The Federalist. 

A Commentary on the Constitution of the United States ; a collection of Essays 
by Alexander Hamilton, Jay, and Madison ; also the Continentalist and other 
papers, by Hamilton. Edited by John C. Hamilton, author of the "History 
of the Republic of the United States." In one vol. 8vo. 

Sloan's .Architectural Works. 

Sloan's Constructive Architecture : A guide for the builder and carpenter; 
exhibiting the construction of a series of designs for roofs, domes, spires, and 
the five orders of architecture, selected from the best specimens of Grecian 
and Roman art, with the figured dimensions of their height, projection, and 
profile. To which is added a treatise on practical geometry. The whole illus- 
trated by 62 plates, and accompanied by explanatory text. By Samuel Sloan, 
Architect, author of the "Model Architect," "City and Suburban Architec- 
ture," etc. etc. One vol. 4to. 

Sloan's City and Suburban Architecture : In which are exhibited numerous 
designs and details for public edifices, private residences, and mercantile build- 
ings. Illustrated with 136 folio engravings, accompanied by specifications, 
and historical and explanatory text. By Samuel Sloan, author of the "Model 
Architect," "Sloan's Constructive Architecture," etc. etc. One vol. folio. 

Sloan's Homestead Architecture : Containing forty designs for villas, cot- 
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ing, furniture, etc. Illustrated with upwards of 200 engravings. By Samuel 
Sloan, Architect. One vol. 8vo. 

illustrated, and will be found of great 
value not only to architects, but to build- 
ers of all classes. The plates which il- 
lustrate and explain the text are drawn 
with rare skill, and are superb speci- 
mens of engraving. — Evening Transcript. 

Sloan's Constructive Architecture is a 
full and eminently practical treatise on 
the higher branches of carpentry, join- 
ery, and building, and is such a work as 
every builder who is not a mere imitator 
of the plans of others will desire to pos- 
sess. — Boston Journal. 

City and Suburban Architecture is a 
perfect storehouse of knowledge on all 
subjects and details which relate to the 
subject of architecture. * * * It will 
serve the student as well as the master, 
for it furnishes an abundance of informa- 
tion as to the early progress of archi- 
tecture, and the rapid stride of improve- 
ment in modern times. — Boston Post. 



The first of these works is adapted to 
the wants of the practical builder and 
mechanic, presenting in natural succes- 
sion numerous examples of forms gener- 
ally esteemed the most useful in con- 
structive carpentry. The second is de- 
voted mainly to city architecture, con- 
taining a great number of designs and 
illustrations for public edifices, private 
residences, and mercantile buildings. 
Each volume is illustrated by a great 
variety of elegant engravings, and be- 
sides the value of the reading matter, 
which to a great extent is founded on the 
personal experience of the author, in 
point of typographical finish and beauty 
is a model of tasteful and attractive ex- 
ecution. — N. Y. Tribune. 

Sloan's Constructive Architecture is 
one of the very best and most elegant 
books on architecture that has appeared 
from the American press. It is prepared 
in the clearest manner, and beautifully 



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Chauvenefs Astronomy. 

A Manual of Spherical and Practical Astronomy, emltracing the General Prob 
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and the Theory and Use of Fixed and Portable Astronomical Instruments. 
With an Appendix on the "Method of Least Squares." Illustrated by en- 
gravings on wood and steel. By William Chauvenet, Professor of Mathe- 
matics and Astronomy in Washington University, St. Louis. 2 vols. Royal 
8vo. §10.00. 

•Army of the Cumberland. 

Annals of the Army of the Cumberland, comprising Biographies, Descriptions of 
Departments, Accounts of Expeditions, Skirmishes, and Battles; also its Po- 
lice Record of Spies, Smugglers, and Prominent Rebel Emissaries, together 
with Anecdotes, Incidents, Reminiscences, etc., and Ofi&cial Reports of the 
Battle of Stone River. By an Officer. Illustrated with numerous Steel 
Portraits, Engravings, and Maps. 8vo. 

Marks' s Peninsular Campaign. 

The Peninsular Campaign in Virginia; or, Incidents and Scenes on the Battle 
Fields and in Richmond. Illustrated with numerous engravings. By Rev. 
J. J. Mabks, D.D., Chaplain of the 63d Pennsylvania Regiment. 12mo. $1.50. 

Cassin's Jlmerican Ornithology. 

American Ornithology; giving a General Synopsis of North American Orni- 
thology, and containing Descriptions and Figures of all North American Birda 
not given by former American Authors, after the manner, and designed as a 
continuation of the Works of Audubon. By John Cassin, Member of the 
Academy of Natural Sciences of Philadelphia, etc. etc. Illustrated with fifty 
beautifully-colored Plates. One vol. 8vo. 

Cassin' s Mammalogy and Ornithology. 

The Mammalogy and Ornithology of the United States Exploring Expedition, 
under the command of Commodore Wilkes. Prepared under the superintend- 
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vol. quarto, with a Folio Atlas of over fifty colored Engravings. $50.00. 
Only 150 copies of this work published. 



Baird's Birds of North America. 

The Birds of North America: The descriptions of species based chiefly on the 
collections in the Museum of the Smithsonian Institution. By Spencer F. 
Baird, Assistant Secretary of the Smithsonian Institution ; with the co-opera- 
tion of John Cassin, of the Academy of Natural Sciences of Philadelphia, and 
Geo. N. Lawrence, of the Lyceum of Natural History of New York. With an 
Atlas of one hundred plates. Text, one vol. 4to., $5.00; Atlas, one vol. 4to., 
$15.00. 



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RandaWs Life of Jefferson. 

The Life of Thomas Jefferson. By Henry S. Randall, LL.D. In 3 vols. 8vo. 
Illustrated by Portraits and other Engravings on Steel, a View of Monticello, 
and various fac-similes, including the Original Draft of the Declaration of 
Independence. 



This Life of Mr. Jefferson is, in every 
sense, an authorized work. It was un- 
dertaken under the approbation of his 
family, with an unreserved access to 
and use of all the private papers of Mr. 
Jefferson in their possession, and has 
received the benefit of their recollections 
and opinions at every step. The purely 
original matter comprises about one- 
third of the work. In the department 
of the biography, embracing some ma- 
terials which have already been pub- 



lished, it has been Mr. Randall's aim, as 
often as practicable, to present Mr. 
Jefferson's own words. The work con- 
tains his expressions on perhaps every 
great question which arose from his ad- 
vent in public life to his death, — a pe- 
riod of about sixty years, and embracing 
the whole foeminq period of the Repub- 
lic. The work contains, besides Mr. 
Jefferson's heretofore unpublished fam- 
ily correspondence, selections from his 
finest published letters, state papers, etc. 



Carey's Social Science, 

The Principles of Social Science. 



By Henry C. Carey, LL.D. In 3 vols. 8vo. 



Of his system it may be truly said 
that, although the study of political 
economy dries up narrow minds and re- 
iiices their vision on earth to goods and 
sales and profits, this study must ever be, 
for minds nobly endowed, a source of 
exalted meditation upon the means of 
ameliorating the lot of the human family, 
and upon the blessings vouchsafed by 



the Eternal Author of all good. — North 
American. 

However the reader may sometimes 
join issue with the logic or recoil from 
the conclusions of this production, it 
will never be without respect for the 
signal ability displayed by the writer in 
this difficult walk of scientific litera- 
ture. — National Intelligencer. 



Great Truths by Gh*eat Authors. 

A Dictionary of Aids {o Reflection, Quotations of Maxims, Counsels, Cautions, 
Aphorisms, Proverbs, etc. etc., from Writers of all Ages and both Hemispheres. 
1 vol. demi 8vo. 

Thiers' s Consulate and Empire of Napoleon. 

The History of the Consulate and Empire of France under Napoleon. By M. 
Adolphe Thiers, late Prime Minister of France, Member of the French 
Academy and of the Institute. Complete in 5 vols. 8vo. 



The Publishers have the pleasure of 
announcing that this great work of M. 
Thiers is completed, — the concluding 
volume (V.) having just been issued 



uniform with the volumes preceding. 
Either of the volumes will be furnished 
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Beck's Medical Jurisprudence. 

Elements of Medical Jurisprudence. By Theodrio Romeyn Beck, M.D., LL.D., 
and John B. Beck, M.D. Twelfth edition. With Notes by an association of 
the friends of Drs. Beck. The whole revised by C. R. Gilman, M.D., Professor 
of Medical Jurisprudence in the College of Physicians and Surgeons of New 
York. 2 vols. 8vo. 



From Prof. J. W. Fo\tler, LL.D., Principal " State 
and National Law School," Poughkeepsie, N. Y. 

* * * It should be in the possession 
of all who desire a ready access to this 



most interesting and important branch 
of Legal Science, a knowledge of which 
is essential to professional success. 



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Scotfs Waverley Novels. 

In various styles, including — 

I. An Abbotsford Edition. — Complete in twelve volumes, demi octavo, with 
illustrations. 

II. A Royal Octavo Illustrated Edition. — In twelve volumes, splendidly 
illustrated with over 300 engravings, comprising Landscapes, Incidents, and 
Portraits of the Historical personages described in the Works. 

III. A Pictorial Edition. — In twenty-four volumes, duodecimo, illustrated 
with over 300 steel and wood engravings. 

IV. A People's Edition. — Complete in six volumes, octavo, illustrated. 

V. A New and Beautifully Illustrated Edition. — In forty-eight volumes, 
cap 8vo., printed on a beautiful Long Primer Type, and illustrated with over 
1500 wood-cuts and steel engravings. (Published in connection with the 
Messrs. A. & C. Black, of Edinburgh.) 

JominVs Art of War. 

The Art of War. By Baron de Jomini, General and Aid-de-Camp of the Em- 
peror of Russia. A new edition, with appendices and maps. Translated from 
the French by Captain Gr. H. Mendell, U.S.A., Corps of Topographical En- 
gineers, and Lieutenant W. P. Ckaighill, U.S.A., Corps of Engineers. One 
vol. demi 8vo. $1.50. 



While everybody is criticising the war, 
would it not be well for somebody to 
read this greatest of military critics, 
and know a mere smattering about the 
matters so dogmatically discussed ? * 



* * * It might be convenient occa- 
sionally in conversation to back up an 
opinion by an allusion to the Baron de 
Jomini. It must be confessed that he 
knows something about war. — Con. Courant. 



Manual for Courts Martial. 

A manual for Courts Martial: Containing full explanations of the duties of all 
officers employed on such service, and complete forms of proceedings, with 
an Appendix and Index. By Captain Henry Coppee, late Instructor in the 
Military Academy at West Point. 18mo. 

Chambers's Encyclopsedia. 

A Dictionary of Universal Knowledge for the People, on the basis of the latest 
edition of the German Conversations-Lexicon. Illustrated with Maps and 
numerous wood Engravings. Published in parts and volumes. The whole to 
be comprised in nine volumes, royal 8vo. Vol. VII. just published. 
Steel-plate Maps, beautifully printed in colors, to illustrate the geographical 
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The Maps for Vol. I. are seven in number, price § .50 
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" *' " " VI. '• two " " 
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WORKS OF JAMES MADISON. 
Letters and Other Writings of James Madison, 

FOURTH PRESIDENT OF THE UNITED STATES. 

IN FOUR VOLUMES. PRICE $16.00. 
Now First Published, 

On the 31st of May, 1848, Congress passed an act appropriating $25,000 to pur- 
chase from Mrs. Madison all the unpublished MSS. of her husband. 

The works thus purchased have been embodied in the four volumes now offered to 
the public, which contain letters of Mr. Madison from 1769 to 1836, together with 
some important additions, among which are Mr. Madison's celebrated ''Examination 
of the British Doctrine," etc., written in 1806; his pamphlet entitled "Political 
Observations," published 1775; some "Essays," chiefly political; the "Virginia 
Proceedings of 1798," etc., etc.; together with Mr. Madison's "Statements in Rela- 
tion to Secretaries Smith and Armstrong;" his Apologue of "Jonathan and Mary 
Bull;" his "Memorandum of Bollman's Interview with President JeflFerson concern- 
ing Burr's Conspiracy;" his "Letter on Napoleon's Return from Elba;" his "Note 
for the Princess," now Queen Victoria; and his "Advice to my Country." The 
whole edited under the direction of the Joint Committee on the Library of Congress. 

Elliot's Debates on the Constitution. 

The Debates in the Several State Conventions on the Adoption of the Federal 
Constitution, as recommended by the General Convention at Philadelphia, 1787. 
Together with the Journal of the Federal Convention, Luther Martin's Letter, 
Yates's Minutes, Congressional Opinions, Virginia and Kentucky Resolutions 
of 1798-99, and other Illustrations of the Constitution. Including the 

UTadison Papers, containing the Debates on the Adoption of the Federal Con- 
stitution in the Convention held at Philadelphia in 1787, with a Diary of the 
Debates of the Congress of the Confederation, as reported by James Madison. 
Published under the sanction of Congress. By Jonathan Elliot. Complete 
in five vols. 8vo. $15.00. 
A very important work, illustrating the history of the Constitution, and exhibit- 
ing the opinions of the ablest statesmen in the country on its several provisions at 
the time when its adoption by the States was under consideration. The Journal of 
(he Convention throws great light on this subject, inasmuch as it makes us acquainted 
with the real intentions of the framers of the Constitution, as indicated by the pro- 
ceedings, from day to day, till the great work was completed. The other illustra- 
tions of the Constitution contained in these volumes are of scarcely less interest 
and importance. 

Schoolcraft's Great National Work. 

Archives of Aboriginal Knowledge, containing all the original papers laid 
before Congress respecting the History, Antiquities, Language, Ethnology, Picto- 
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States. Numerous illustrations. 6 vols, imperial quarto. 



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Bitter's Comparative Geography. 



Comparative Geography. By Carl Ritteb, late Professor of Geography in the 
University of Berlin. Translated by Rev. William L. Gage. 12mo. $1.50. 

SUMMARY OF CONTENTS. 

Introduction. Introductory Remarks — The Earth as the Dwelling-place of 
Man — Geography as a Science — What Geographical Science has yet to accomplish 
— Sources of Geographical Science — The Sciences Illustrative of Geography. 

Part First, The Surface of the Earth considered in its most General 
Relations. — The Spheroidal Form of the Earth — The Threefold Covering of the 
Earth — The Superficial Dimensions of the Land and Water on the Globe — Contrast 
of the Land and AVater Hemispheres — The Position of the Continents and its Influ- 
ence on the Course of History — The Pyramidal Forms of the Great Land-masses 
and their Southward Direction toward the Oceanic Hemisphere — Situation of the 
Continents in their Relation to each other and to their collective whole — The 
Historical Element in Geographical Science. 

Part Second. A More Extended Investigation Regarding the Earth's 
Surface. — Highlands or Plateaus — Mountains and Mountain Lands — The Rela- 
tions of Plateau Systems — Primeval Formation of Plateaus and Mountains — Origin 
of Plateaus — Origin of Mountains — Lowlands — Middle European Lowland — Origin 
of the Great Central European Plain — The Ponto-Caspian Plain — Origin of Ponto- 
Caspian Depression — Depression of the Jordan Valley and of the Dead Sea — Bitter 
Lakes of the Suez Isthmus — Regions of Transition between Highlands and Low- 
lands: the River Systems of the Globe — Terrace Lands and Rivers — Upper, Middle, 
and Lower Course of Rivers — Historical Influence of Plateaus — Influence of River 
Systems on Civilization. 

Part Third. Configuration of the Continents. — Superficial Dimensions and 
Articulation of the Continents — Islands — Results of the above considerations briefly 
stated— The New World. 

From James Pyle Wickersham, A.M., 

Principal of the Pennsylvania State Normal Scfiaol 

at MiUersville. 



I have read Ritter's "Comparative 
Geography," as translated by William 
L. Gage, with very great satisfaction. 
It is a comprehensive, compact, and clear 
statement of the great principles of geo- 
graphical science. Geography, as pre- 
sented in our ordinary treatises, is not 
at all a science, but merely a collection 
of facts and fragments. In this book, 
however, all details find their proper 
place in a philosophical system. No 
teacher of geography should be without 
the book. 

From the California Teacher. 
This volume consists of the courses of 
lectures by Ritter before the University 
of Berlin, and contains much reliable 
information which can be used in the 
school-room daily by any active teacher. 
Ritter was the first, we think, to show to 
the world that geography was a science 
of relations, and not a mere mass of 



unorganized facts, as the relation of a 
country to its national life, and to the 
civil structure or State. He treated it 
as an organized unity, and made the 
Earth the home of man — the theater of 
soul, and mind, and character. He 
thought that every people was the re- 
flection of the country which it inhab- 
ited. The Introductory Lecture is worth 
alone the price of the volume, as it re- 
veals his whole plan of treatment of 
geography, as a prominent and distinct 
science, and shows how insignificant 
have been our ideas of it hitherto. We 
heartily recommend it te all teachers. 
From the New York Teacher. 
Mr. Gage could not have done a better 
service to American students than that 
of giving them, in their own vernacular, 
this elementary treatise, by the greatest 
of the German geographers. This book 
is a complete though elementary treatise 
on physical geography, and will be found 
a valuable aid to teachers and advanced 
students. 



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Climatology of the United States. 

Climatology of the United States, and of the Temperate Latitudes of the North 
American Continent; embracing a full comparison of these with the Climatology 
of the Temperate Latitudes of Europe and Asia; with Isothermal and Rain 
Charts, including a summary of Meteorological Observations in the United 
States, condensed from recent scientific and official publications. By Lorin 
Blodget, author of several Reports on American Climatology. One vol. large 
octavo. $5.00. 

Scribner on Dower. 

A Treatise on the Law of Dower, embracing the Common Law and the Statutory 
Provisions and Judicial Decisions of England and the several United States 
upon that subject. 2 vols. 8vo. Vol. I. $6.00; Vol. II. in press. 

The Loves and Heroines of the Poets, 

By Richard Henry Stoddard. Illustrated with real and ideal portraits from de- 
signs by Barry and others, in steel, of Petrarch's Laura, Tasso's Leonora, Surry's 
Geraldine, Jonson's Celia, Shakspeare's "Love," Waller's Sacharissa, Pope's 
Martha Blount, Byron's Maid of Athens, Burns's Highland Mary, Coleridge's 
Genevieve, Longfellow's Minnehaha, Tennyson's Maud. 1 vol. 4to. 

Wood and Bache^s Dispensatory. 

The Dispensatory of the United States of America. By George B. Wood, M.D., 
President of American Philosophical Society, etc , etc., and Franklin Bache, 
M.D., late Professor of Chemistry in Jeflferson Medical College, etc., etc. 
Twelfth edition, carefully revised. 1 vol. 8vo. 



"Some idea may be formed of the 
amount of new matter added to the Dis- 
pensatory in this revision when it is un- 
derstood that, notwithstanding the very 
considerable space gained by the con- 
solidation of the three British Pharma- 
copoeias into one, and the consequent 
substitution, in many instances, of a 



single process and its necessary com- 
mentary for three, and notwithstanding 
the elFort made to compress everything 
to be said into the fewest possible words, 
and to leave no part of the space unoc- 
cupied, it has nevertheless been found 
necessary to extend the limits of the 
work by more than one hundred pages." 



Thomas'" s Pronouncing Medical Dictionary, 

A Comprehensive Medical Dictionary, containing the Pronunciation, Etymology, 
and Signification of the Terms made use of in Medicine and the Kindred Sci- 
ences. With an Appendix, comprising a complete list of all the more important 
articles of the Materia Medica, arranged according to their medicinal properties ; 
also an explanation of the Latin Terms and Phrases occurring in Anatomy, 
Pharmacy, etc.; together with the necessary directions for writing Latin Pre- 
scriptions, etc., etc. By J. Thomas, M.D., author of the System of Pronun- 
ciation in "Lippincott's Pronouncing Gazetteer of the World." Demi 8vo. 
Cloth, $3.00; leather, $3.50. 



From Dr. W. H. Yan Buken. 
I regard Dr. Thomas's Comprehensive 
Medical Dictionary as the best diction- 
ary of its size within the reach of the 
student and practitioner. Its directions 
for the pronunciation of Latin terms and 



for the correct writing of prescriptions 
are especially valuable and complete. 
In typography and arrangement of mat- 
ter it is admirable. 

W. H. VAN BUREN, M.D., 
Professor Anatomy, University New York, 



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